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
driver/i2c: additional docu for pull resistors
Merge pull request #2200 from haukepetersen/fix_i2c_doc

driver/i2c: additional docu for pull resistors
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
driver/timer: adjusted doxygen for speed value
Merge pull request #2202 from haukepetersen/fix_driver_timerdoc

driver/timer: adjusted doxygen for speed value
board/mbed_lpc1768: added timer definitions
cpu/lpc1768: added basic timer implementation
Merge pull request #2168 from haukepetersen/add_lpc1768_timer

cpu/lpc1768: added basic timer implementation
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