cpu/cc2538 bug fix: OE (output enable) bit was set by gpio_init_in().
timex: make functions static inline

This commit makes all one- or two-liners in timex a static inline
function, defined in the header file.
timex: replace print by a to_str function

Instead of printing the timestamp, it's more flexible to convert it into
a string.
timex: update copyrights
timex: remove redundant struct timex_t declaration

timex_t is available as a typedef, declaring it as `struct timex_t` in
addition is not necessary.
make: fix make targets buildtest and info-boards-supported

Fixes issues with the make targets buildtest and info-boards-supported
on OS X hosts. Comments and recommentations to simplify and beautify
would be appreciated.
drivers - cc110x: rename cc110x to cc110x_legacy_csma
drivers - cc110x_legacy_csma: add missing license
Merge pull request #1894 from thomaseichinger/buildtest_fix

make: fix make targets buildtest and info-boards-supported
Merge pull request #1874 from locicontrols/cc2538-oe

cpu/cc2538 bug fix: OE (output enable) bit was set by gpio_init_in().
doc: compliment and fix timex documentation
Merge pull request #1880 from fnack/cc110x_rename

drivers/cc110x: rename driver to cc110x_legacy_csma
Merge pull request #1843 from OlegHahm/timex_cleanup

sys: timex cleanup