RFC: changing variable naming rules in LLVM codebase

The issue here is that neither of us is a new contributor, but we're
trying to guess what it would be like for someone new. It may seem that
long names make it easier, but when I started with LLVM I actually found
the naming convention (and the use of abbreviations) very appealing.

As a somewhat new contributor to clang, I agree with the above. What the
abbreviations means is very easy to pick up and it let me concentrate on
the structure of the code.

But independently of this I would like to express the fact that a change
of naming convention is very disruptive for what seems to me a minor gain.
Yes there are some inconsistencies across all of the sub-projects but
is that really such a big problem ? The two proposed solutions (big-bang
change and gradually over time) both in general would be quite disruptive
and would be annoying with git blame.