Use argc and argv in shell handlers

Compare #708.

Now the tokenization of an input line is done by the shell itself. You
may quote arguments with `"..."`. Empty arguments, supplied by `""` are
preserved. Spaces in between arguments are squasheds; spaces inside
quotes are preserved.

You cannot partially quote an argument. You must not use
- `cmd "abc`,
- `cmd abc"def"`, or
- `cmd "abc"def`.
Print error message on any quoting error
Convert examples
Do not skip over the null terminator
Fix _settime_handler
shell: adapt register prefix command to new shell api
Fix libcoap make
added gettimeofday syscall

RIOT's gettimeofday needs to be called from syscalls.c to assure that gcc actually links it.

If an RTC if available and enabled it will be used instead.
fixed typo
Adds test for pthread.

The test uses pthread to calculate the factorial of 12, with one
thread for each multiplication. pthread_mutex is used for synchronization.
Add a mechanism for handling fatal errors (and reboots)
Implement the crash-handling/reboot mechanism for MSP430 MCUs
Implemented crash-handling mechanism for 'native' platform
Implemented the crash-handling/reboot mechanism for ARM-based MCUs
LPC1768 implementation of 'core_panic()'
copied from 'arm_common', for make-related reasons...
add mutex_unlock_and_sleep()
add test for mutex_unlock_and_sleep()