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.
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
ccnl: added documentation and proper event handling for dropped packets
posix: added sleep and usleep
test: added test case for posix sleep
Merge pull request #839 from mehlis/posix-sleep

posix: added sleep and usleep
Merge pull request #832 from mehlis/ccn-lite-follow-up-11

ccnl: added documentation and proper event handling for dropped packets
Merge pull request #806 from Kijewski/sem-pthread-native

native/posix: Don't include sys/types.h in semaphore.h
Merge pull request #794 from Kijewski/shell-args-escape

shell: Allow escaped characters in shell
Merge pull request #698 from Kijewski/thread_wakeup-dint

Changes to `thread_wakeup`
Merge pull request #820 from Kijewski/expect-sha256

tests: Add automatized test for sha256
add mutex_unlock_and_sleep()
add test for mutex_unlock_and_sleep()
Fix `pthread_mutex_lock()` check in test_pthread_cooperation
Merge pull request #728 from BytesGalore/add_unlock_mutex_and_sleep

core:mutex: enable atomic execution of unlock a mutex and sleep for a thread
Merge pull request #849 from Kijewski/issue-844

posix: Fix `pthread_mutex_lock()` check in test_pthread_cooperation
Auto init source address mode
Merge pull request #852 from authmillenon/autoinit-src-addr-mode

net_if/auto_init: Auto init source address mode