Inital commit of stm32f4xx framework.

stm/.gitignore

stm/Makefile

stm/delay.s

stm/fatfs/diskio.c

stm/fatfs/diskio.h

stm/fatfs/ff.c

stm/fatfs/ff.h

stm/fatfs/ffconf.h

stm/fatfs/integer.h

stm/flash.c

stm/font_petme128_8x8.h

stm/lib/core_cm4.h

stm/lib/core_cm4_simd.h

stm/lib/core_cmFunc.h

stm/lib/core_cmInstr.h

stm/lib/stm32f4xx.h

stm/lib/stm32f4xx_conf.h

stm/lib/stm32f4xx_dma.c

stm/lib/stm32f4xx_dma.h

stm/lib/stm32f4xx_exti.c