And removed nearly all xub_StrLen in starmath.

Some sal_uInt16 which were xub_StrLen before
9a0d753b are also converted to sal_Int32
where applicable.

Change-Id: I31d7794f4c7aa840545edff41a102b76bb39e042
Reviewed-on: https://gerrit.libreoffice.org/5817Reviewed-by: Andrzej J.R. Hunt <andrzej@ahunt.org>
Tested-by: Andrzej J.R. Hunt <andrzej@ahunt.org>