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/proto/strings.pro b/src/proto/strings.pro
index b792edc..c25555f 100644
--- a/src/proto/strings.pro
+++ b/src/proto/strings.pro
@@ -17,6 +17,7 @@
 int vim_strnicmp(char *s1, char *s2, size_t len);
 int vim_strnicmp_asc(char *s1, char *s2, size_t len);
 char_u *vim_strchr(char_u *string, int c);
+char *vim_strnchr(const char *p, size_t *n, int c);
 char_u *vim_strbyte(char_u *string, int c);
 char_u *vim_strrchr(char_u *string, int c);
 void sort_strings(char_u **files, int count);