Unit tests

[rene0]

Add unit tests for all functions in libdcf77. Perhaps if a test is difficult to write/run, the corresponding function needs to be refactored.

Testing the GPIO pin reading needs some live tests to read a 0 pulse and a 1 pulse for example. This part is probably platform specific (which platforms to keep?)

• test for DST/leap announcements
• bits1to14.h
• calendar.h
• decode_alarm.h - not done, no proper specifications
• decode_time.h (split up?)
• input.h (except for get_bit_live() )
• mainloop.h - we have dcf77pi[-analyze].c and readpin.c for this
• setclock.h