Implement blargg ntsc filters

- this implements blargg's nes ntsc filters using core options
- an optional height doubling is also added but disabled for performance reasons (might make that optional as a core option)
- since PS2 and PSP have their own blitter branches, these platforms do not have the ntsc filters since i dont have the means to test on those systems.
- compile with HAVE_NTSC=1 to have these options, HAVE_NTSC=0 disabled filter including core options
- HAVE_NTSC=1 is set as default, other than PS2 and PSP as stated above.

Makefile.common

@@ -17,6 +17,11 @@ else
 SOURCES_C = $(CORE_DIR)/boards/*.c $(CORE_DIR)/input/*.c
 endif
 
+ifeq ($(HAVE_NTSC),1)
+CFLAGS += -DHAVE_NTSC_FILTER -I$(CORE_DIR)/ntsc
+SOURCES_C += $(CORE_DIR)/ntsc/nes_ntsc.c
+endif
+
 ifeq ($(HAVE_GRIFFIN),1)
 SOURCES_C += $(CORE_DIR)/drivers/libretro/griffin.c
 else