Support for STM32F7 -- second part

miosix/arch/common/drivers/serial_stm32.cpp

miosix/arch/common/drivers/serial_stm32.h

miosix/arch/cortexM7_stm32f7/common/arch_settings.h

...x/arch/cortexM7_stm32f7/common/interfaces-impl/delays.cpp

...rch/cortexM7_stm32f7/common/interfaces-impl/gpio_impl.cpp

.../arch/cortexM7_stm32f7/common/interfaces-impl/gpio_impl.h

...h/cortexM7_stm32f7/common/interfaces-impl/portability.cpp

...ortexM7_stm32f7/common/interfaces-impl/portability_impl.h

...cortexM7_stm32f7/stm32f746zg_nucleo/core/stage_1_boot.cpp

.../stm32f746zg_nucleo/interfaces-impl/arch_registers_impl.h

...rtexM7_stm32f7/stm32f746zg_nucleo/interfaces-impl/bsp.cpp

...xM7_stm32f7/stm32f746zg_nucleo/interfaces-impl/bsp_impl.h

miosix/arch/cortexM7_stm32f7/stm32f746zg_nucleo/openocd.cfg

...rtexM7_stm32f7/stm32f746zg_nucleo/stm32_1024k+256k_rom.ld