Add '.so' to the list of file extensions cleared up by 'make clean' in

Makefile.cyg, since if you're building against Winelib it will
generate one of those alongside each .exe file.


git-svn-id: svn://svn.tartarus.org/sgt/putty@9952 cda61777-01e9-0310-a592-d414129be87e

mkfiles.pl

@@ -492,7 +492,7 @@ sub manpages {
     print "\n";
     print $makefile_extra{'cygwin'}->{'end'};
     print "\nclean:\n".
-    "\trm -f *.o *.exe *.res.o *.map\n".
+    "\trm -f *.o *.exe *.res.o *.so *.map\n".
     "\n".
     "FORCE:\n";
     select STDOUT; close OUT;