*_stdup_printf -> strdup for "single string only" formatting.

*_stdup_printf -> strdup for "single string only" formatting.

Done for performance improvements.

This could probably be done in checkAPIs.pl, but this was just
a quick manual check with grepping.

Change-Id: I91ff102cb528bb00fa2f65489de53890e7e46f2d
Reviewed-on: https://code.wireshark.org/review/15751
Reviewed-by: Michael Mann <mmann78@netscape.net>
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Jaap Keuter <jaap.keuter@xs4all.nl>