patch 8.0.0643: when a pattern search is slow Vim becomes unusable

Problem:    When 'hlsearch' is set and matching with the last search pattern
            is very slow, Vim becomes unusable.  Cannot quit search by
            pressing CTRL-C.
Solution:   When the search times out set a flag and don't try again.  Check
            for timeout and CTRL-C in NFA loop that adds states.
diff --git a/src/edit.c b/src/edit.c
index 89a5fae..da1b238 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -4512,7 +4512,7 @@
 		    found_new_match = searchit(NULL, ins_buf, pos,
 							      compl_direction,
 				 compl_pattern, 1L, SEARCH_KEEP + SEARCH_NFMSG,
-						  RE_LAST, (linenr_T)0, NULL);
+					     RE_LAST, (linenr_T)0, NULL, NULL);
 		--msg_silent;
 		if (!compl_started || set_match_pos)
 		{