native: implement hwtimer removal
applications: set stack size correctly

The correct stack size for all examples and test applications correctly.
KERNEL_CONF_STACKSIZE_MAIN is the correct stack size for any thread
using printf.

Also adapted black lists accordingly.
sys/ps: s/float/int for runtime

The high precision isn't needed, use per mille instead.
Circumvents printf problems on some platforms.

Also: prevent division by zero.
sys/ps: fix comment style, superfluous declaration
Merge pull request #1370 from OlegHahm/fix_stack_sizes

applications: set stack size correctly
Merge pull request #1352 from LudwigOrtmann/nofloat

sys/ps: don't use float for runtime calculations
Merge pull request #1351 from LudwigOrtmann/native_hwtimer

native: implement hwtimer removal
native: override INCLUDES w/ NATIVEINCLUDES

Currrently native overrides the object file targets, because it needs
the different include paths to interact with libc and the OS.

This PR simplifies their makefiles to only override the variable
INCLUDES, instead of overriding the targets.