connectivity: harmonize types relatated to Tell()/Seek()

Change-Id: I032f6d32b151203e62b23bffaf25dbc4aeb5ae8a
Reviewed-on: https://gerrit.libreoffice.org/8217
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>