In some cases, type lookup has to deal with situations where it cannot...

In some cases, type lookup has to deal with situations where it cannot reconstruct a compile unit or a function, but it still has a valid symbol - and it can use that in order to figure out the preferential language for lookups

This is not the right thing for all clients (notably the expression parser), so put it in type lookup specific code

Fixes rdar://problem/22422313

llvm-svn: 269095