Document the "calling" macros for the strtmpl.cxx template file.
And remove unnecessary use of those macros in the calling file.

Change-Id: I20e0dd74150773363b9fb557884b84692ce22f11
Reviewed-on: https://gerrit.libreoffice.org/6504Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>