patch 9.1.1009: diff feature can be improved

Problem:  diff feature can be improved
Solution: include the linematch diff alignment algorithm
          (Jonathon)

closes: #9661

Signed-off-by: Jonathon <jonathonwhite@protonmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/globals.h b/src/globals.h
index 77ddea8..e3b1e27f 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -869,6 +869,7 @@
 #ifdef FEAT_DIFF
 // Value set from 'diffopt'.
 EXTERN int	diff_context INIT(= 6);		// context for folds
+EXTERN int      linematch_lines INIT(= 0);      // number of lines for diff line match
 EXTERN int	diff_foldcolumn INIT(= 2);	// 'foldcolumn' for diff mode
 EXTERN int	diff_need_scrollbind INIT(= FALSE);
 #endif