Exclude *.c files from make doc
Introduce macro to define files that should be deleted on make clean
Move .elf file to it's own target
Make directory creation in object compilation more makey
make: put buildtest goals into an own file

`Makefile.include` is too long as is.
make: delete everything in buildtest beforehand
make: supply `-j` on `buildtest`

We support `make -j` for a while now. `make buildtest` takes ages to
finish. So just supply `-j` on buildtest.
Merge pull request #1169 from Kijewski/buildtest-minus-j

make: supply `-j` on `buildtest`
shell: renaming `isnumber` to `is_number` in sc_net_if.c

fix name collision on OS X by renaming
net: handle macro redefinitions for OS X

undefine macros and reorder header includes to get rid of system
defined macros on OS X

fixes #1165
make: Remove `Makefile.unsupported`

This mechanism was replaced by #535. It was only used in one project.
Merge pull request #1137 from authmillenon/no_c_doc

doc: Exclude *.c files from make doc
Merge pull request #1098 from authmillenon/make-addon

make: Make make more flexible
Merge pull request #1173 from thomaseichinger/fix_rpl_udp_osx

native: net: OSX: Fix rpl_udp example
Merge pull request #1174 from Kijewski/remove-Makefile.unsupported

make: Remove `Makefile.unsupported`
boards: fix license headers to LGPL

harmonises license headers in msb-430, msba2-common,
msba2 and wsn430-common

fixes #1160
Merge pull request #1176 from thomaseichinger/fix_1160

boards: fix license headers to LGPL
license checker WIP