Changes to `thread_wakeup`

`thread_wakeup` did not check if target pid is invalid.

`thread_wakeup` used `dINT` and `eINT` directly.
It should use `disableIRQ` and `restoreIRQ` instead, because there might
be other (good) reasons why one might want to call `thread_wakeup` with
interrupts disabled.

`thread_wakeup` yielded even if the other thread had a lower priority
than the current thread.
Allow escaped characters in shell

Per #708.

This patch allows escaped characters in the shell, and makes the
apostrophe a quotation mark. The escape character is backslash.

The term "escape character" is used liberally in here: if a backslash is
encountered in the command line, the next character will be taken
verbatim. No escape sequences are understood, i.e. `"\n"` is just the
letter `n`, not a new line.
Don't build PKGs twice
Don't use INCLUDES for building any native at all.

native modules will never need the dynamic INCLUDES, so we define our
own NATIVEINCLUDES. Due to the current make structure, the only way to
not use INCLUDES is to redefine the build rules.
native/posix: Don't include sys/types.h in sem

`sys/types.h` contains the native definition for `pthread_*_t`. This
causes clashes if you want to use `semaphore` and `pthread` in the same
application.
Add automatized test for sha256
sys/crypto: remove assert.h include

It is not used and most platforms don't have it.
test_net_if/Makefile remove superfluous includes
Remove useless assert comments

address: https://github.com/RIOT-OS/RIOT/pull/824#issuecomment-36426297
Merge pull request #824 from LudwigOrtmann/3des_includes

sys/crypto: remove assert.h include
Merge pull request #802 from Kijewski/dont-build-pkgs-twice

Make: Don't build PKGs twice
Merge pull request #826 from LudwigOrtmann/test_net_if_cleaning

test_net_if/Makefile remove superfluous includes
enhanced RPL debugging
RPL byte order issues
Merge pull request #805 from OlegHahm/rpl_fixes

RPL: byte order fixes and debugging
ccnl: added documentation and proper event handling for dropped packets
removed error causing packed attribute in net_if
removed obsolete buffer
Merge pull request #833 from OlegHahm/net_if_fix

sys: net: net_if fix
pthread: mutex - return the right values