make: del no-delete-null-pointer-checks for clang++

This PR enables the use of clang++ to compile C++ projects by adding
`CXXUWFLAGS += -fno-delete-null-pointer-checks`, if `${CC}` understands
`-fno-delete-null-pointer-checks` but `${CXX}` does not.
make: fix the order of Makefile.dep for timex

The order of modules in Makefile.dep matters.
make: fix dependencies

uart0 depends on POSIX, not the other way around.
posix: configure stdio only to uart0 if enabled
boards/iot-lab_M3: fix PORT
Merge pull request #1754 from OlegHahm/timex_makefile_order

make: fix the order of Makefile.dep for timex
Merge pull request #1773 from thomaseichinger/fix_iot-lab_term

boards/iot-lab_M3: fix PORT for TERM
netdev: Provide maximum value of netdev_opt_t for further definitions
Merge pull request #1774 from authmillenon/netdev-opt-max

netdev: Provide maximum value of netdev_opt_t for further definitions
netdev.tests: Add fixes for environment variables

+ minor include fix
netdev.tests: Kill processes properly
cpu: Implement SPI driver for sam3x8e
boards: Implement SPI definitions for arduino-due
Merge pull request #1778 from authmillenon/netdev-test-env-fixes

netdev.tests: Add fixes for environment variables
Merge pull request #1584 from PeterKietzmann/add_sam3x_spi

cpu/board: updated  spi driver for arduino-due
boards/iot-lab_M3: change to openocd's new ftdi interface

Openocd communication was done over a deprecated interface definition,
namely ft2232. Using the new ftdi interface speeds up flashing and
doesn't throw warnings anymore.
native/freebsd: fix tapsetup permission
native/freebsd: fix usecond typdef
Merge pull request #1729 from Kijewski/clang++

make: del no-delete-null-pointer-checks for clang++
nativenet: Apply coding conventions