patch 9.1.0766: too many strlen() calls in ex_getln.c

Problem:  too many strlen() calls in ex_getln.c
Solution: refactor the code to reduce the number of strlen() calls
          (John Marriott)

closes: #15809

Signed-off-by: John Marriott <basilisk@internode.on.net>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/proto/search.pro b/src/proto/search.pro
index 8665994..f450d09 100644
--- a/src/proto/search.pro
+++ b/src/proto/search.pro
@@ -8,6 +8,7 @@
 void save_last_search_pattern(void);
 void restore_last_search_pattern(void);
 char_u *last_search_pattern(void);
+size_t last_search_pattern_len(void);
 int ignorecase(char_u *pat);
 int ignorecase_opt(char_u *pat, int ic_in, int scs);
 int pat_has_uppercase(char_u *pat);