patch 8.2.0681: pattern for 'hlsearch' highlighting may leak

Problem:    Pattern for 'hlsearch' highlighting may leak. (Dominique Pelle)
Solution:   Call end_search_hl() to make sure the previous pattern is freed.
            (closes #6028)

src/screen.c

@@ -1718,6 +1718,7 @@ start_search_hl(void)
 {
     if (p_hls && !no_hlsearch)
     {
+	end_search_hl();  // just in case it wasn't called before
 	last_pat_prog(&screen_search_hl.rm);
 	screen_search_hl.attr = HL_ATTR(HLF_L);
 # ifdef FEAT_RELTIME

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    681,
 /**/
     680,
 /**/