Add (very partial) Kate syntax highlighting definition for TableGen

This is very clearly not very good, and is very partial.
But this is better than nothing at all, and shouldn't
hurt those who don't need it.

If there are others interested in this functionality,
it will be great to further improve this.

{F6253091}

Reviewed By: Bigcheese

Differential Revision: https://reviews.llvm.org/D47080

llvm-svn: 337415