MINOR: contrib: Make the wireshark peers dissector compile for more distribs.

MINOR: contrib: Make the wireshark peers dissector compile for more distribs.

With a 2.6.8 wireshark, this module could not compile because of ws_version.h
missing header. This patch offers the possibility to compile this plugin without
having to include this header. Furthermore with my wireshark version a
"plugin_release" object is required to make it be loaded by wireshark. This is
a string which seems to have to match a dotted string made of you wireshark
major and minor versions.