native profiling support

only works with Linux for now
change target name, add cachegrind target
rebase_fixup
make: streamline native targets

The new target names are easier to remember / decipher:

term
term-cachegrind
term-gprof
term-valgrind

all
all-cachegrind
all-gprof
all-valgrind
all-debug

eval-gprof
eval-cachegrind
add variables for gprof, cg_annotate
Prepend path to dependency info files with sed

The old way was error prone due to it's use of a fixed path file and
confusing.

closes #775
pipe through sed instead

addresses: https://github.com/RIOT-OS/RIOT/pull/778#discussion_r10041955
change new/overlooked Makefiles
remove some newlines
examples/hello-world: return instead of busy loop.
Merge pull request #973 from LudwigOrtmann/examples_hello-world_update

examples/hello-world: return instead of busy loop.
Merge pull request #789 from LudwigOrtmann/native_gprof

native profiling tools support
Fix dereferencing of type-punned pointer

Fixes #897
Add `pthread_barrier_*` functions

Compare [`pthread_barrier_init`][1].

  [1]: http://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_barrier_init.html
Add pthread_barrier test
Add pthread_barrier_t documentation
gitignore cachegrind.out
Merge pull request #988 from Kijewski/ignore-cachegrind.out

gitignore: add cachegrind.out
Merge pull request #778 from LudwigOrtmann/dependency_files

Make: Prepend path to dependency info files with sed
Merge pull request #914 from authmillenon/fix-dereferencing

net: sixlowpan: Fix dereferencing of type-punned pointer