patch 9.1.0689: [security]: buffer-overflow in do_search() with 'rightleft'

Problem:  buffer-overflow in do_search() with 'rightleft'
          (SuyueGuo)
Solution: after reversing the text (which allocates a new buffer),
          re-calculate the text length

Github Advisory:
https://github.com/vim/vim/security/advisories/GHSA-v2x2-cjcg-f9jm

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/search.c b/src/search.c
index 01c143f..e5936d8 100644
--- a/src/search.c
+++ b/src/search.c
@@ -1548,6 +1548,7 @@
 			{
 			    vim_free(msgbuf);
 			    msgbuf = r;
+			    msgbuflen = STRLEN(msgbuf);
 			    // move reversed text to beginning of buffer
 			    while (*r != NUL && *r == ' ')
 				r++;