Also remove some useless math/DSP headers.
The USB code really needed updating, considering the following entries from ST's
release notes (
https://raw.github.com/STMicroelectronics/STM32CubeF0/master/Release_Notes.html
) :
-Bug fix: USB_ReadPMA() and USB_WritePMA() by ensuring 16-bits access to
USB PMA memory
-Bug fix: correct USB RX count calculation
-Fix USB Bulk transfer double buffer mode