quick patch for gitk-1.1

It turns out that Linus' linux-2.6 tree now has a commit in it with
one of the parents listed twice, which confuses gitk and causes it to
stop with an error.  I have a new version of gitk almost ready to go,
but in the meantime here is a quick patch for gitk-1.1 to fix the
problem.

The confusing commit is 13e652800d1644dfedcd0d59ac95ef0beb7f3165.

Paul.

--- gitk~	2005-06-01 18:14:51.000000000 +1000
+++ gitk	2005-06-19 21:55:02.000000000 +1000

@@ -582,6 +582,7 @@
 	set ofill white
 	if {[info exists parents($id)]} {
 	    foreach p $parents($id) {
+		if {[lsearch -exact $actualparents $p] >= 0} continue
 		if {[info exists ncleft($p)]} {
 		    incr ncleft($p) -1
 		    if {![info exists commitinfo($p)]} {