Development environment setup:

This works for me.  YMMV.

Install wireshark source tree:

% tar -xjvf /tmp/wireshark-1.2.2.tar.bz2 

Within the wireshark tree, check out p25 plugin from op25:

% cd wireshark-1.2.2/plugins
% svn checkout http://www.sedition.org.au/svn/op25/trunk/wireshark/plugins/p25

A few small changes need to be made to the wireshark tree outside of the
plugins directory.  Apply a patch to accomplish this:

% cd ..
% patch -p1 <../op25/wireshark/patches/wireshark-1.2.2.patch 

Update the build tree with these changes and compile:

% ./autogen.sh 
% ./configure
% make