avsextrem: use cc110x_ng as default transceiver driver
tests: remove `test_` prefix

Closes #1485.
tests: fix APPLICATION name
Merge pull request #1503 from phiros/avsextrem_default_transceiver_cc110x_ng

avsextrem: use cc110x_ng as default transceiver driver
Merge pull request #1502 from Kijewski/issue-1485

tests: remove `test_` prefix
make: force traversal into PKG's, same as normal modules
pkg: add USEPKG module "libfixmath"

This PR adds the USEPKG module "libfixmath".
It integrates https://code.google.com/p/libfixmath/ into RIOT, cmp. #1457.