Rework interaction between AnalysisContext and CFG::BuildOptions to keep a...

Rework interaction between AnalysisContext and CFG::BuildOptions to keep a BuildOptions object around instead of keeping a copy of the flags.

Moreover, change AnalysisContext to use an OwningPtr for created analysis objects instead
of directly managing them.

Finally, add a 'forcedBlkExprs' entry to CFG::BuildOptions that will be used by the
CFGBuilder to force specific expressions to be block-level expressions.

llvm-svn: 127385