This was a good idea from mike kaganski as a consequence of
   https://gerrit.libreoffice.org/55359

Unfortunately, clang/llvm is not yet up to the job of doing floating
point evaluation, I get tons of crashes all over the evaluate
infrastruction inside clang, so this will need to wait until clang's
code matures.

So park it in store for now

Change-Id: I5ba4de8323e462b4fd4db301e4d116a81fd56ed3
Reviewed-on: https://gerrit.libreoffice.org/59254
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>