Added K20D5M support
Merge branch 'master' into K20D50
K20 uVision files, ld NVIC offset

	- K20 KEIL files
	- clock set to 1 (48MHz)
	- offset in GCC ld for vectors in RAM
	- us ticker - PIT timer interrupt implementation
startup ARM - stack pointer, serial functional

	- stack pointer correction
	- startup for ARM - clean up
	- GCC ARM linker - RAM size correction
	- NVIC - RAM address
Analog API - pins, analog pins (arduino) correction, irq

	- ADC - pins, mux
	- analog pins - Ax
	- irq - port A - E
nRF51822 mbed SDK with working GPIO, RawSerial, and timer
pwm, spi - pin definition, dac removed
Bogdan's startup fix added.
Merge branch 'master' into K20D50
Port, Buffer, DigitalInOut, and Spi (master) works.
The python script provided in the original repo fails trying to access an empty string as a file, this version removes any empty strings in the files to build.
NUCLEO_F103RB: Add I2C master api
Added RTS/CTS flow control

Currently implemented only for LPC1768. On this platform, when hardware
flow control is not directly supported, it will be emulated.
Also added "not_implemented.c" as a placeholder for various HAL functions
that might not be implemented on all platforms (in this particular case,
serial_set_flow_control). These are weak implementations that default to a
"not implemented" error message.
Fixed RTS/CTS bit-banging on LPC1768
Added flow control test

Since this requires a separate serial port connection, added this as a
new attribute of the MUTs.
Hardware flow control implementation for LPC81X
SPISlave works. pwm_out works but needs more work to properly implement 0 pulse and 100% pulse.
SPISlave works.
Add \r in retarget
PwmOut working.