Provide a common clock initialization driver rather than leaving
clock initialization to the boards code. A declarative description of
the board's clock configuration using a struct does still allow to
fine-tune settings. In addition, a board is still allowed to just
provide a custom `void clock_init(void)` if there really is the need
to do crazy things.
- most were trivial
- missing group close or open
- extra space
- no doxygen comment
- name commad might open an implicit group
this hould also be implicit cosed but does not happen somtimes
- crazy: internal declared groups have to be closed internal
* also added a trailing underscore to header guards for consistency
Commit for PR 2623, repairing header file include guards.
This PR is intended to fix the include guards in files under RIOT/boards
SQUASH ME: fix underscore removal overdos
SQUASH ME: consistent macro naming
SQUASH ME: missed that one
SQUASH ME: fixed overdo
SQUASH ME: consistency
