Clean up math functions

- Remove checking for standard functions from the build system
- Prefix all invocations with std::
- Replace suffixed functions with unprefixed versions
- Include <cmath> in all files that use it and remove the global include

e.g. floorf(x) -> std::floor(x)

src/Background.cpp

@@ -17,13 +17,14 @@
 #include "ThemeMetric.h"
 #include "PlayerState.h"
 #include "ActorUtil.h"
-#include <float.h>
 #include "XmlFile.h"
 #include "XmlFileUtil.h"
 #include "BackgroundUtil.h"
 #include "Song.h"
 #include "AutoActor.h"
 
+#include <cfloat>
+
 static ThemeMetric<float> LEFT_EDGE				("Background","LeftEdge");
 static ThemeMetric<float> TOP_EDGE				("Background","TopEdge");
 static ThemeMetric<float> RIGHT_EDGE				("Background","RightEdge");