MSP430: Add "counter" driver

#include <msp430.h>

#include <stdint.h>

class Counter {

	private:

		Counter(const Counter &copy);

	public:

		uint8_t overflowed;

		Counter() : overflowed(0) {}

		inline void start() {

			overflowed = 0;

			TA2CTL = TASSEL__SMCLK | ID__1 | MC__CONTINUOUS;

			TA2EX0 = 0;

			TA2CTL |= TACLR;

		}

		inline uint16_t stop() {

			TA2CTL = 0;

			return TA2R;

		}

};

extern Counter counter;

	CXX_TARGETS += src/arch/msp430fr5969lp/driver/timer.cc

endif

ifneq ($(findstring counter,${arch_drivers}), )

	CXX_TARGETS += src/arch/msp430fr5969lp/driver/counter.cc

endif

ifneq (${cpu_freq}, )

	COMMON_FLAGS += -DF_CPU=${cpu_freq}UL

else

#include "driver/counter.h"

#if defined(TIMER_CYCLES)

#warn "timer_cycles and counter are mutually exclusive. Expect odd behaviour."

#endif

Counter counter;