Build system changes to use TableGen to generate the various

diagnostics. This builds on the patch that Sebastian committed and
then revert. Major differences are:

  - We don't remove or use the current ".def" files. Instead, for now,
    we just make sure that we're building the ".inc" files.
  - Fixed CMake makefiles to run TableGen and build the ".inc" files
    when needed. Tested with both the Xcode and Makefile generators
    provided by CMake, so it should be solid.
  - Fixed normal makefiles to handle out-of-source builds that involve
    the ".inc" files.

I'll send a separate patch to the list with Sebastian's changes that
eliminate the use of the .def files.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@67058 91177308-0d34-0410-b5e6-96231b3b80d8