Draft: Supporting witness export for backward analysis
git-svn-id: https://svn.sosy-lab.org/software/cpachecker/branches/963-backward-analysis-witness@43529 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c
In this MR, exporting ARGs constructed by a backward analysis is implemented. It is the first milestone of the Google Summer of Code project by Bas Laarakker.
This MR is only for code review. Merging has to be done via SVN.
Closes #963