#273 header for pin manipulation (for EFM8BB1)

[Kharitonov Dmitry]

header for pin manipulation.
for example

#include "portpins.h"
#define PWM_PIN     P1_0

pin_set_output(PWM_PIN);
pin_set_input_analog(PWM_PIN);
pin_set_output_open_drain(PWM_PIN);
pin_toggle(PWM_PIN);
pin_write(PWM_PIN,1);

[Maarten Brock]

portpins.h redefines true & false, NULL, __bit, and just disables some warnings.
IMO therefor we cannot accept this patch.