git-gui: handle "deleted symlink" diff marker

Signed-off-by: Michele Ballabio <barra_cuda@katamail.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
diff --git a/lib/diff.tcl b/lib/diff.tcl
index 9eeff2e..a1d5e52 100644
--- a/lib/diff.tcl
+++ b/lib/diff.tcl
@@ -203,6 +203,7 @@
 		if {[string match {mode *} $line]
 			|| [string match {new file *} $line]
 			|| [string match {deleted file *} $line]
+			|| [string match {deleted symlink} $line]
 			|| [string match {Binary files * and * differ} $line]
 			|| $line eq {\ No newline at end of file}
 			|| [regexp {^\* Unmerged path } $line]} {