Parser: Extended the functionality of parseStatements.

Changed the interface of CParser, Scope is now requiered, but may be an
empty CProgramScope. 

Added Scope interface to be able to reuse generated types when parsing
single statement.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@12962 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c