This improves and unifies our approach to printing all template
arguments.
The same approach to printing types is extended to all
TemplateArguments: A sugared version is printed in quotes, followed by
printing the canonical form, unless they would print the same.
Special improvements are done to add more detail to template template
arguments.
It's planned in a future patch to use this improved TemplateName printer
for other places besides TemplateArguments.
Note: The sugared/desugared printing does not show up for TemplateNames
in tests yet, because we do a poor job of preserving their type sugar.
This will be improved in a future patch.
This implementation takes quite a bit from the OMP implementation of
array sections, but only has to enforce the rules as applicable to
OpenACC. Additionally, it does its best to create an AST node (with the
assistance of RecoveryExprs) with as much checking done as soon as
possible in the case of instantiations.
