Clean up getTime helpers

This increases size of the getTime return values to 64 bits.
It also removes the TimeGetter classes since the getTime functions
are now very precise.

src/porting.cpp

@@ -942,5 +942,18 @@ void attachOrCreateConsole(void)
 #endif
 }
 
+// Load performance counter frequency only once at startup
+#ifdef _WIN32
+
+inline double get_perf_freq()
+{
+	LARGE_INTEGER freq;
+	QueryPerformanceFrequency(&freq);
+	return freq.QuadPart;
+}
+
+double perf_freq = get_perf_freq();
+
+#endif
 
 } //namespace porting