C Instrumentation Framework

Since master branch of Aspectator submodule serves for merging original sources of GCC to Aspectator and C-backend (that are placed to branches aspectator and c-backend respectively) it would be well to protect it from writing. Otherwise one can push aspectator branch to master unintentionally and it will be unpleasant work to remove it from there. For instance I have already merged aspectator branch to local master branch several times.