Avoid O(n^2) loop in SwXFrame::setPropertyValue, we even have an index
to search for this stuff
Reduces load time from 325s to 172s
Change-Id: I6c6c03206ef81be1d7d7702a4313acd23d75442d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/165044
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>