[STM32F3-Discovery][DISCO_F303VC] initial port.

Hello,

I've ported mbed-sdk to STM32F3-Discovery(STM32F303VC) board.
This port is basically derived from NUCLEO_F302R8 port
and ported only with GCC_ARM toolchain at the momemt.

The target name is 'DISCO_F303VC'.

The statement at this moment is as follows,
I've checked working well,
(1) Simple 'ticker' program 'MBED_11: Ticker with printf() out to UART' is ok.
PA2: UART TX
PA3: UART RX
(3) MBED_5: PWM
PWM port are PA_8,PA_9
Period 20msec, duty 50% and 75% are ok.
(4) wait_us() function, 100usec is ok.

NUCLEO_F302R8(STM32F302R8) and STM32F3-Discovery(STM32F303VC) have
very similar peripheral architecture,
so probably some other peripheral test will be pass.

Build method:
(1) Build mbed library
python workspace_tools/build.py -m DISCO_F303VC -t GCC_ARM
(2) Generate test project (i.e.)
python workspace_tools/project.py -m DISCO_F303VC -i gcc_arm -p 39
(3) Build test project
Unzip
build/export/MBED_11_gcc_arm_DISCO_F303VC.zip
and execute command line 'make'.

Would you merge this implementation ?

By the way I know about STM32F3XX port.
I think in the future STM32F3XX port and DISCO_F303VC port should be united
its folder structure and files like LPC11XX / LPC11CXX port. 


dinau