F4 USB: Don't enable IN endpoints when configuring.
F4: Added more timer instances.
Build rules: Use -std=gnu+++11.
Add SPI_t::transfer_byte().
Added timers to F3.
Added basic HID descriptors.
Removed GPIO handling from I2C driver.
Moved Pin class into GPIO_t class.
Added PinArray class.
Added generic HID driver class.
Added F1/F3 SPI definitions.
Make Firmware builder take linker arguments.
Don't call rcc_init() at startup.
Add DFU descriptors.
HID: added set_feature_report().
Added PinArray::set_type().
HID: added get_feature_report().