changed/added names of board definitions
Added LD memory maps for STM32F302 line
F3-port: Added HIGH_DENSITY and XL_DENSITY defines for STM32F30x series to libmaple
F3-port: Added missing STM32F302x and STM32F303x make targets
F3-port: wirish bugfix, SPI3 is available on all F302 and F303 densities
F3-port: use pin names and PIN_MAP to enable and disable debug ports
F3-port: build targets for all supported F302 and F303 MCUs