patch 9.1.1520: completion: search completion doesn't handle 'smartcase' well

Problem:  When using `/` or `?` in command-line mode with 'ignorecase' and
          'smartcase' enabled, the completion menu could show items that
          don't actually match any text in the buffer due to case mismatches

Solution: Instead of validating menu items only against the user-typed
          pattern, the new logic also checks whether the completed item
          matches actual buffer content. If needed, it retries the match
          using a lowercased version of the candidate, respecting
          smartcase semantics.

closes: #17665

Signed-off-by: Girish Palya <girishji@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 76c51ab..a892dcb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -720,6 +720,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1520,
+/**/
     1519,
 /**/
     1518,