insure that we have an entire match for the variable name

Pick up patch from Samba:

    commit fa331f64d1a40350496c7acf68c20cb3fead6eaf
    Author: Matthieu Patou <mat@matws.net>
    Date:   Thu Oct 3 09:45:19 2013 -0700

    pidl-wireshark: insure that we have an entire match for the variable name

Change-Id: I1e730dfb3b9eb96a4cda34659297fddeac7801c8
Reviewed-on: https://code.wireshark.org/review/5095
Reviewed-by: Guy Harris <guy@alum.mit.edu>