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