Using precompiled header have significant performance benefit
on windows, and seems to be quite stable
let's seclect it by default.

Change-Id: Ia3d0ea53007e3550e819acdd7943bed945887bd0
Reviewed-on: https://gerrit.libreoffice.org/15045Tested-by: Jenkins <ci@libreoffice.org>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>