pidl/ws: Fix Dead Store (Dead assignement/Dead increment) warning found by Clang

pidl/ws: Fix Dead Store (Dead assignement/Dead increment) warning found by Clang

Port Wireshark commit f0b5fb7

Author: Alexis La Goutte <alexis.lagoutte@gmail.com>
Date:   Fri Sep 26 21:31:32 2014 +0200

    PIDL: Fix Dead Store (Dead assignement/Dead increment) warning found by Clang

    Change-Id: I7f6f974732b7905f4ea4686e1a79ca6fbef78fa8
    Reviewed-on: https://code.wireshark.org/review/4319
    Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>
Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: David Disseldorp <ddiss@samba.org>