Move traverseunqualifiedtypeloc over to the 'main' typeloc tree.

Move traverseunqualifiedtypeloc over to the 'main' typeloc tree.
Note that this is a move -- we pretend that we were really looking
at the unqualified typeloc all along -- rather than a recursion, so
we don't follow the normal CRTP plan of going through
getDerived().TraverseTypeLoc.  If we did, we'd be traversing twice
for the same type (once as a QualifiedTypeLoc version of the type,
once as an UnqualifiedTypeLoc version of the type), which in effect
means we'd call VisitTypeLoc twice with the 'same' type.  This
solves that problem, at the cost of never seeing the qualified
version of the type (unless the client subclasses
TraverseQualifiedTypeLoc themselves).  It's not a perfect solution.
A perfect solution probably requires making QualifiedTypeLoc a
wrapper around TypeLoc -- like QualType is a wrapper around Type*
-- rather than being its own class in the type hierarchy.

Reviewed by wan.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@107973 91177308-0d34-0410-b5e6-96231b3b80d8