Fix all warnings for native and qemu-i386

Missing returns, unused variables (only used for debugging), empty
translation units, missing function prototypes, and GNU extensions.
nativenet: change max packet size to 127

Real IEEE 802.15.4 transceivers have a payload of 127. Hence, for
testing - particular 6lowpan - it would make sense to have the same
limitation in nativenet. Especially to test fragmentation this is
helpful.
cpu - sam3x8e: added switch for newlib-nano specs
Merge pull request #1354 from OlegHahm/nativenet_packetsize

nativenet: change max packet size to 127
Merge pull request #1335 from Kijewski/fix-all-warnings-for-native-and-qemu-i386

Fix all warnings for native and qemu-i386
Merge pull request #1356 from haukepetersen/fix_sam3x_newlibnano

cpu - sam3x8e: added switch for newlib-nano specs
Merge pull request #1357 from haukepetersen/fix_cortexm3_threading

cpu: cortex-m3_common: cleanup thread_arch.c
Introducing a source routing header for RPL.
Merge pull request #1218 from fabianbrandt/srh_rpl

Introducing a source routing header for RPL.
cpu:cortex_common: add core_panic function
cpu: initial import of stm32f1
cpu:stm32f1: license cleanup and restructuring
cpu:stm32f1: add st header definitions
compiles but doesn"t link
intermediate commit
change to cortex_m3_common
change to cortex-m3_common
removed all *not* needed header files
intermediate commit, some fixes to timer
board - iot-lab_M3: restructuring and clean-up