convert xub_StrLen to sal_Int32

convert for loops using xub_StrLen to use sal_Int32

Change-Id: I5f635ca078966fefe938dbc7e8dea7c8d0d0b554
convert xub_StrLen to sal_Int32

convert various module-local functions

Change-Id: I89f3eb40b107e2617958e474ffe86bd73e01cf33
convert INetMIMEOutputSink::write from xub_StrLen to sal_Int32

Change-Id: I923a6cb4ee6641c9a289e28c32f431ba6c38d5dc
convert linguistic::isUpper from xub_StrLen to sal_Int32

Change-Id: I7bf426e1753b3761c9ce8930ad637526a9895495