Objective-C++ (and c++) Sema: Patch fixes a sema crash when gnu’s ?: extension

is used for Objective-C++’s dictionary subscripting. This is done by filtering
out all placeholder types before check on lowering of the
common expression is done. // rdar://1374918.
Reviewed by John McCall.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182120 91177308-0d34-0410-b5e6-96231b3b80d8