Load correct shared object name in python.

This fixes following error message shown by wireshark/tshark when wireshark-devel

was not installed:

   libwireshark.so: cannot open shared object file: No such file or directory

diff -up wireshark-1.6.0/epan/wspython/wspy_libws.py.soname wireshark-1.6.0/epan/wspython/wspy_libws.py

--- wireshark-1.6.0/epan/wspython/wspy_libws.py.soname	2011-06-09 14:40:04.562726728 +0200

+++ wireshark-1.6.0/epan/wspython/wspy_libws.py	2011-06-09 14:40:09.775467946 +0200

@@ -35,7 +35,7 @@ def get_libws_libname():

   elif system == "Windows":

     return 'libwireshark.dll'

   else:

-    return 'libwireshark.so'

+    return 'libwireshark.so.2'

 def get_libws_handle():

   global __libwireshark