Remove historical Unicode TODOs

There's no immediate demand or plan to work on these.
Begin RAV reunification: s/DataRecursiveASTVisitor/RecursiveASTVisitor/

Define a macro to reduce the delta between RecursiveASTVisitor and
DataRecursiveASTVisitor.

Some years ago, someone thought it was a good idea to copy the entire RAV to
support cursor visitation in libclang.

Since then the two have diverged needlessly and the rest is history.

This series of commits aims to reduce delta between the two so that we can
reason about their differences, apply bugfixes that were only made to one but
not the other, and ultimately find a way to unify two two chunks of code.
Format the two RecursiveASTVisitors

Apply current ToT clang-format on the two RAVs to reduce delta and help
identify differences between the two.

We lose a little pretty formatting in the headers but that's the price to pay
so we can diff these two files effectively and look to a future where we don't
have to maintain two copies of this code.

Formatting and whitespace only.
Ongoing RAV reunification

 * Shuffle around code to reduce delta between the two RAVs.
 * Merge r189185 that was applied only to one of the RAVs and became apparent during the unification work.
 * Fix Enqueue data recursion typo.

Our delta is down to +-579!