stm32f4: Document which discovery board the examples are for

Try and reduce a little confusion if we can.
Update the library to the newest version
example for MSC (Mass Storage Class) support
MSC: Use another PID to load correct drivers
Use libopencm3 coding style
stm32f4: drop dead code from usb example.

Presumably code that attempted to toggle a led, but it wasn't setup, and it's
not in any other examples.  Kill it for now.

Reported-by: stefanct on irc.
Update upstream library.
Update upstream library
Update library for new gpio_toggle
stm32/l1: lcd: example using the LCD
Update library to get spi fix
lib: Update to fetch latest l0/f0 updates.
stm32:l0: miniblink example

Very basic, as all miniblinks.
stm32f4: usb_midi: Introduce example MIDI firmware

Tested on STM32F4Discovery with Linux host using both amidi (raw
messages to/from device) and a synthesizer (note on/off).