got HID working:
 - usbd_register_control_callback called twice (each call specifies a single type of control request only I think)
 - the HID TLC read/write only seems to work when it has endpoint address 1 & 2
update makefile for stm32f4discovery specific commands
Merge branch 'cdcacm' of https://github.com/djpnewton/kowhai_stm32f4 into cdcacm