Squelch some compiler warnings.

Change-Id: I768bf577b3871171ab33f080c5a0099ac06718ce
Reviewed-on: https://code.wireshark.org/review/2906
Reviewed-by: Guy Harris <guy@alum.mit.edu>
(cherry picked from commit 0a2f6fc01a9170ffc29570436c5496c046612a56)
Reviewed-on: https://code.wireshark.org/review/2927