Refactoring: Parsing strings must be centralized at one location
such that we can easily change it.
Never parse the same string in more than one location!
Also, do not hard-code values such as the default value of an SSAMap in
other places.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@14254 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c