Initialize the error-reporting routines before scanning for plugins, as

Initialize the error-reporting routines before scanning for plugins, as
the code to scan for them uses those routines.

This means epan_init() no longer takes those routines as arguments -
which is just as well, given that the mechanism in question is no longer
part of libwireshark, but is part of libwsutil.

This should fix bug 9508.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@53796 f5534014-38df-0310-8fa8-9805f1628bb7