shell: print command if not found
shell: fixup test_shell expect scripts
shell: fix newlines
x86: add read-before-write check at runtime

Finding read-before-writes statically is quite difficult. In native we
can use valgrind, but on boards without an MMU we are out of luck.

x86 has an MMU, let's use it.

If `-DDEBUG_READ_BEFORE_WRITE` was set, then pages on the heap get
initialized upon first use. If the page was read before written, then a
debug message with the virtual and physical address of the memory
location is printed, as well as the address of the offending instruction.
you can never have enough debugging in RPL
some minor fixes and debugging
set correct transceiver stack size for debugging
fixed debugging for cc110x
net: IPv6: RPL: more debug output
rpl: debug: use DEBUGF where necessary
tests: add test_vtimer_msg_diff

This test sets three timers and renews them periodically, showing the
difference they accumulate.
tests: test_vtimer_msg_diff: use array for timers, change first to 1s
tests: test_vtimer_msg_diff: add some timers, change max values
tests: test_vtimer_msg_diff: Makefile s/PROJECT/APPLICATION/g
cpu: added low-level pwm driver impl for lpc2387
boards: added periph_conf.h for msba2 and avsextrem
drivers: added rgbled driver
drivers: some adjustments to low-level pwm driver

- adjusted doxygen and boilerplate
- changed return values for start and stop functions
board - pttu: added periph_conf.h
native: remove some warnings about undef functions

This PR implements `real_X` for `X in (fork, dup2, unlink, execve)`.
These function caused warnings while making the default example.