AST Matchers Reference missing from 3.8.0 rc1 and 2

http://llvm.org/pre-releases/3.8.0/rc2/tools/clang/docs/LibASTMatchersReference.html ought to have the reference, but it’s not there. I think this is the same problem as on trunk where html files are not getting copied as part of the sphinx generation.

I noticed this Sunday and submitted a patch, but it should also go in the rc, or equivalent, if the way I did it isn’t good cmake.

See [PATCH] D16963: Copy LibASTMatchersReference.html to gen’d docs