Add 60FPS overclock hack

Let's see, this should fix issues on platforms that do not support
running the emu at 59.73 FPS. We run the emu at fake 60fps, which means
we produce more audio samples than the original device.

Instead of missing samples (which produce cracks in the audio) we should
be producing some extra samples, which will result in a frame drop every
now and then (like every minute or so, so it's not noticeable).

Makefile

@@ -222,7 +222,7 @@ else ifeq ($(platform), vita)
 	TARGET := $(TARGET_NAME)_libretro_$(platform).a
 	CC = arm-vita-eabi-gcc$(EXE_EXT)
 	AR = arm-vita-eabi-ar$(EXE_EXT)
-	CFLAGS += -DVITA
+	CFLAGS += -DVITA -DOVERCLOCK_60FPS
 	CFLAGS += -marm -mcpu=cortex-a9 -mfloat-abi=hard
 	CFLAGS += -Wall -mword-relocations
 	CFLAGS += -fomit-frame-pointer -ffast-math

libretro/libretro.c

@@ -51,7 +51,7 @@ static int translation_caches_inited = 0;
 #define MAX_PATH (512)
 #endif
 
-// 59.72750057 hz
+// Usually 59.72750057 Hz, unless GBC_RATE is overclocked (for 60FPS)
 #define GBA_FPS ((float) GBC_BASE_RATE) / (308 * 228 * 4)
 
 /* Maximum number of consecutive frames that

sound.h

@@ -25,7 +25,11 @@
 
 #define GBA_SOUND_FREQUENCY   (64 * 1024)
 
-#define GBC_BASE_RATE ((float)(16 * 1024 * 1024))
+#ifdef OVERCLOCK_60FPS
+  #define GBC_BASE_RATE ((float)(60 * 228 * (272+960)))
+#else
+  #define GBC_BASE_RATE ((float)(16 * 1024 * 1024))
+#endif
 
 #define DIRECT_SOUND_INACTIVE         0
 #define DIRECT_SOUND_RIGHT            1