Remove most trivial Eclipse warnings.
Please follow our style guide and keep CPAchecker free of warnings.
These trivial warnings make it hard for every developer
to see the actually critical warnings.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@13989 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c