The primary goal here is to make the type node hierarchy available to
other tblgen backends, although it should also make it easier to generate
more selective x-macros in the future.
Because tblgen doesn't seem to allow backends to preserve the source
order of defs, this is not NFC because it significantly re-orders IDs.
I've fixed the one (fortunately obvious) place where we relied on
the old order. Unfortunately, I wasn't able to share code with the
existing AST-node x-macro generators because the x-macro schema we use
for types is different in a number of ways. The main loss is that
subclasses aren't ordered together, which doesn't seem important for
types because the hierarchy is generally very shallow with little
clustering.
llvm-svn: 373407
a82d2fe944