Record CC and CXX in config.status.

This patch also adds the CC and CXX environment variables to the config.status
command in the build directory. When invoking ./build/config.status without
this extra environment variable, one might not end up with the same build
environment as in the first build.
Merge pull request #120 from mavam/master

Record CC and CXX in config.status.
Merge branch 'master' into unstable