Ensure canonical type is actually canonical.

ASTContext::applyObjCProtocolQualifiers will return a canonical type when given
a canonical type and an array of canonical protocols.  If the protocols are not
canonical then the returned type is also not canonical.  Since a canonical type is needed, canonicalize the returned type before using it.  This later prevents
a type from having a non-canonical canonical type.

llvm-svn: 341013