Revert r156142, "[libclang] Bring back BodyIndexer::TraverseCXXOperatorCallExpr which"

It caused test/Index/index-many-call-ops.cpp to fail in stage2 c-index-test on selfhosting i686-cygwin and x86_64-linux since r156229 (Reverting making RecursiveASTVisitor data recursive).

llvm-svn: 156253