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/WheelNotifyIcon.cpp

@@ -86,9 +86,10 @@ void WheelNotifyIcon::Update( float fDeltaTime )
 		/* We should probably end up parsing the vector and then dynamically
 		 * insert flag icons based on "priority". Easy to do, hopefully
 			- Midiman */
-		const float fSecondFraction = std::fmod( RageTimer::GetTimeSinceStartFast(), 1 );
-		const int index = (int)(fSecondFraction*m_vIconsToShow.size());
-		Sprite::SetState( m_vIconsToShow[index] );
+        static std::uint_fast32_t updateCounter = 0;
+        updateCounter++;
+        const int index = updateCounter % m_vIconsToShow.size();
+        Sprite::SetState(m_vIconsToShow[index]);
 	}
 
 	Sprite::Update( fDeltaTime );