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.
diff --git a/contrib/wireshark-dissectors/peers/README b/contrib/wireshark-dissectors/peers/README
index 78cafcd..83b57d2 100644
--- a/contrib/wireshark-dissectors/peers/README
+++ b/contrib/wireshark-dissectors/peers/README
@@ -37,6 +37,16 @@
 
 $ make
 
+It is possible that depending on your distribution the compilation may fail
+with such an error:
+
+  packet-happp.c:40:10: fatal error: ws_version.h: No such file or directory
+                #include <ws_version.h>
+
+In this case try to build this plugins with this OPTS variable:
+
+$ OPTS=-DWITHOUT_WS_VERSION make
+
 To install it in your home directory:
 
 $ make install