Switch the interface name for both TemplateTypeParmType and

SubstTemplateTypeParmType to be 'getIdentifier' instead of 'getName' as
it returns an identifier. This makes them more consistent with the
NamedDecl interface.

Also, switch back to using this interface to acquire the indentifier in
TypePrinter.cpp. I missed this in r130628.

llvm-svn: 130629