Preliminary support for LPC13XX

Works only with GCC_ARM for now.
[LPC1347]: first implementation of PWMOut (not tested)
[LPC1347]: first implementation of analogIn (not tested)
[LPC1347] Added GPIO interrupts
[LPC1347]: first implementation of USB device (not tested)
[LPC1347] Added support for the ARM toolchain.
[LPC1347] Change LED pin names
[LPC1347]: add support for RTOS
Added support for UART break generation.
[LPC11U24] Take advantage of the full 8K of RAM

The linker command scripts/startup files used only 4K of RAM on this target.
mbed_interface_disconnect/powerdown are now synchronous calls

Fixes PRMBED-804