LPC11U35 support for USBDevice and mbed-rtos

Added support for the EA LPC11U35 QuickStart Board to USBDevice an
mbed-rtos. Also fixed several string-related bugs in USBDevice.
Merge pull request #146 from neilt6/master

LPC11U35 support for USBDevice and mbed-rtos
[NUCLEO_L152RE] Add rtc api
[NUCLEO_F030R8] Add rtc api
Merge branch 'master' of https://github.com/mbedmicro/mbed