libAnalysis: Add a case for TypeAliasDecl in CFGRecStmtDeclVisitor.

Neither of the current clients of CFGRecStmtDeclVisitor are doing
anything with typedefs, so I assume type aliases (C++11 "using")
can be safely ignored. This was causing assertion failures in
the analyzer.

<rdar://problem/13228440>

llvm-svn: 175335