Fix lookup of variables for multiple C files and static functions.
A identifier that was a local variable as well as a static function
was bound to the function instead of to the variable.
This fixes #165.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@13631 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c