The initial version of the patch kit added location wrapper nodes
around constants and uses-of-declarations, along with some other
places in the parser (typeid, alignof, sizeof, offsetof).
This version takes a much more minimal approach: it only adds
location wrapper nodes around the arguments at callsites, thus
not adding wrapper nodes around uses of constants and decls in other
locations.
It keeps them for the other places in the parser (typeid, alignof,
sizeof, offsetof).
In addition, for now, each site that adds wrapper nodes is guarded
with !processing_template_decl, suppressing the creation of wrapper
nodes when processing template declarations. This is to simplify
the patch kit so that we don't have to support wrapper nodes during
template expansion.