Core Text API gives us float bounding box that we round ourselves, on
other platforms we get rounding integers. Try to use the same rounding
on Mac as FreeType does internally, hopefully this is the same on
Windows.

Change-Id: I7eb08464b008174270880575c4f3df28ede5c89d
Reviewed-on: https://gerrit.libreoffice.org/34661Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Khaled Hosny <khaledhosny@eglug.org>