native: move rtc to periph

* adapt implementation to new interface
* remove now superfluous drivers directory
native/rtc: clean up documentation
native/rtc: improve implementation

* add error checking / warnings
* implement parts of alarm functionality
* clean up
native/rtc:  define ENABLE_DEBUG, move include
native/rtc: apply naming conventions
sys/shell: rewrite rtc command for periph/rtc
sys/shell: use more common libc calls

use strtol instead of sscanf
use plain printf instead of asctime
examples/default: use periph/rtc instead of rtc

The rtc module is deprecated and will be removed.
sys/shell: refactor _parse_time
boards: created periph-conf.h for remaining boards
cc430: lpc2387: switch to new periph/rtc interface

Removes the old interface.
rtc: cleanup of lpc2387-rtc implementation
cpu: remove superfluous gettimeofday functions
cpu: lpc2387: further rtc cleanup
periph_rtc: streamline lpc2387 and cc430 naming
travis: make travis happy for empty header files
pttu: add periph_rtc also to this MSB-A2 variant
Merge pull request #2060 from OlegHahm/periph_rtc

drivers: Adapt old platforms to periph rtc