Switch from Float to Integer Time Values

- Use fast data types where possible so the compiler can optimize for speed based on platform
    - for example, 128 bits might be fastest on ARM
    - good future-proofing

- Refactor GetTimeSinceStart() to be a bit faster
    - multiplication is much faster than division

- Implement a RageTimer method to get the seconds value as a plain int, for the places which cast the seconds value to an int

- Changing from GetTimeSinceStartFast() to GetTimeSinceStart() where accuracy is important

- Changing from GetTimeSinceStart() to GetUsecsSinceStart() for timestamp diffs

- Adjust RageThreads to accomodate an unsigned timestamp value
   - a constant for the maximum value of `uint_fast64_t` replaces `-1` to accommodate the change from signed to unsigned for the `locked_at` variable
   - i have separate constants for `std::numeric_limits<std::uint_fast64_t>::max()` and `static_cast<std::uint_fast64_t>(-1)`, so the reader understands -1 represents an error code, though they evaluate to the same value, so i could remove one of the two

- Add two methods to calculate the MMSSMsMs / MMSSMsMsMs time value from usecs directly instead of inferring it from a seconds value, in RageUtil

- Use a similar counter/modulo based method for WheelNotifyIcon, similar to what i did for text_glow in NoteField in 2eeee03

- Make `g_iStartTime` static const for safety

Rename two timer functions:
GetUsecsSinceStart -> GetTimeSinceStartMicroseconds
GetMicrosecondsSinceStart -> GetSystemTimeAsMicroseconds

Remove std prefix from uint_fast64_t

src/arch/ArchHooks/ArchHooks.h

@@ -87,7 +87,7 @@ public:
 	 * underlying timers may be 32-bit, but implementations should try to avoid
 	 * wrapping if possible.
 	 */
-	static std::int64_t GetMicrosecondsSinceStart();
+	static std::int64_t GetSystemTimeInMicroseconds();
 
 	/*
 	 * Add file search paths, higher priority first.
@@ -129,7 +129,7 @@ public:
 	void RegisterWithLua();
 
 private:
-	/* This are helpers for GetMicrosecondsSinceStart on systems with a timer
+	/* This are helpers for GetSystemTimeInMicroseconds on systems with a timer
 	 * that may loop or move backwards. */
 	static std::int64_t FixupTimeIfLooped( std::int64_t usecs );
 	static std::int64_t FixupTimeIfBackwards( std::int64_t usecs );

src/arch/ArchHooks/ArchHooksUtil.cpp

@@ -4,7 +4,7 @@
 #include <cstdint>
 
 /*
- * This is a helper for GetMicrosecondsSinceStart on systems with a system
+ * This is a helper for GetSystemTimeInMicroseconds on systems with a system
  * timer that may loop or move backwards.
  *
  * The time may decrease last for at least two reasons:
@@ -23,7 +23,7 @@
  *
  * This helper only needs to be used if one or both of the above conditions can occur.
  * If the underlying timer is reliable, this doesn't need to be used (for a small
- * efficiency bonus).  Also, you may omit this for GetMicrosecondsSinceStart() when
+ * efficiency bonus).  Also, you may omit this for GetSystemTimeInMicroseconds() when
  * bAccurate == false.
  */
 

src/arch/ArchHooks/ArchHooks_MacOSX.mm

@@ -258,7 +258,7 @@ bool ArchHooks_MacOSX::GoToURL( RString sUrl )
 	return result == 0;
 }
 
-std::int64_t ArchHooks::GetMicrosecondsSinceStart()
+std::int64_t ArchHooks::GetSystemTimeInMicroseconds()
 {
 	// http://developer.apple.com/qa/qa2004/qa1398.html
 	static double factor = 0.0;

src/arch/ArchHooks/ArchHooks_Unix.cpp

@@ -120,7 +120,7 @@ static void TestTLS()
 #endif
 
 #if 1
-/* If librt is available, use CLOCK_MONOTONIC to implement GetMicrosecondsSinceStart,
+/* If librt is available, use CLOCK_MONOTONIC to implement GetSystemTimeInMicroseconds,
  * if supported, so changes to the system clock don't cause problems. */
 namespace
 {
@@ -149,7 +149,7 @@ clockid_t ArchHooks_Unix::GetClock()
 	return g_Clock;
 }
 
-std::int64_t ArchHooks::GetMicrosecondsSinceStart()
+std::int64_t ArchHooks::GetSystemTimeInMicroseconds()
 {
 	OpenGetTime();
 
@@ -162,7 +162,7 @@ std::int64_t ArchHooks::GetMicrosecondsSinceStart()
 	return iRet;
 }
 #else
-std::int64_t ArchHooks::GetMicrosecondsSinceStart()
+std::int64_t ArchHooks::GetSystemTimeInMicroseconds()
 {
 	struct timeval tv;
 	gettimeofday( &tv, nullptr );

src/arch/ArchHooks/ArchHooks_Unix.h

@@ -13,7 +13,7 @@ public:
 	void DumpDebugInfo();
 
 	void SetTime( tm newtime );
-	std::int64_t GetMicrosecondsSinceStart();
+	std::int64_t GetSystemTimeInMicroseconds();
 
 	void MountInitialFilesystems( const RString &sDirOfExecutable );
 	float GetDisplayAspectRatio() { return 4.0f/3; }

src/arch/ArchHooks/ArchHooks_Win32Static.cpp

@@ -39,7 +39,7 @@ static void InitTimer()
 	QueryPerformanceFrequency(&g_liFrequency);
 }
 
-std::int64_t ArchHooks::GetMicrosecondsSinceStart()
+std::int64_t ArchHooks::GetSystemTimeInMicroseconds()
 {
 	// Make sure the timer is initialized.
 	if (!g_bTimerInitialized) {

src/arch/Sound/RageSoundDriver_Generic_Software.cpp

@@ -301,8 +301,9 @@ void RageSoundDriver::Update()
 //		LOG->Trace("set (#%i) %p from STOPPING to HALTING", i, m_Sounds[i].m_pSound);
 	}
 
-	static float fNext = 0;
-	if( RageTimer::GetTimeSinceStart() >= fNext )
+	constexpr uint_fast64_t iUsecs = 1000000;
+	static uint_fast64_t fNextUsecs = 0;
+	if (RageTimer::GetTimeSinceStartMicroseconds() >= fNextUsecs)
 	{
 		/* Lockless: only Mix() can write to underruns. */
 		int current_underruns = underruns;
@@ -314,7 +315,7 @@ void RageSoundDriver::Update()
 
 			/* Don't log again for at least a second, or we'll burst output
 			 * and possibly cause more underruns. */
-			fNext = RageTimer::GetTimeSinceStart() + 1;
+			fNextUsecs = RageTimer::GetTimeSinceStartMicroseconds() + iUsecs;
 		}
 	}
 
@@ -493,7 +494,7 @@ std::int64_t RageSoundDriver::ClampHardwareFrame( std::int64_t iHardwareFrame )
 		/* Clamp the output to one per second, so one underruns don't cascade due to
 		 * output spam. */
 		static std::int64_t lastTime = 0;
-		std::int64_t currentTime = RageTimer::GetUsecsSinceStart();
+		std::int64_t currentTime = RageTimer::GetTimeSinceStartMicroseconds();
 		if( lastTime == 0 || (currentTime - lastTime) > 1000000 )
 		{
 			LOG->Trace("RageSoundDriver: driver returned a lesser position (%" PRId64 " < %" PRId64 ")", iHardwareFrame, m_iMaxHardwareFrame);
@@ -529,9 +530,9 @@ std::int64_t RageSoundDriver::GetHardwareFrame( RageTimer *pTimestamp=nullptr )
 
 	do
 	{
-		iStartTime = RageTimer::GetUsecsSinceStart();
+		iStartTime = RageTimer::GetTimeSinceStartMicroseconds();
 		iPositionFrames = GetPosition();
-		std::uint64_t elapsedTime = RageTimer::GetUsecsSinceStart() - iStartTime;
+		std::uint64_t elapsedTime = RageTimer::GetTimeSinceStartMicroseconds() - iStartTime;
 		if (elapsedTime <= iThreshold) break;
 	} while (--iTries);
 

src/arch/Sound/RageSoundDriver_Null.cpp

@@ -25,7 +25,7 @@ void RageSoundDriver_Null::Update()
 
 std::int64_t RageSoundDriver_Null::GetPosition() const
 {
-	return std::int64_t( RageTimer::GetTimeSinceStart() * m_iSampleRate );
+	return (RageTimer::GetTimeSinceStartMicroseconds() * m_iSampleRate) / 1000000;
 }
 
 RageSoundDriver_Null::RageSoundDriver_Null()