make: Remove `Makefile.unsupported`

This mechanism was replaced by #535. It was only used in one project.
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