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/proto/regexp.pro b/src/proto/regexp.pro
index dfe5c91..d22a83b 100644
--- a/src/proto/regexp.pro
+++ b/src/proto/regexp.pro
@@ -16,5 +16,5 @@
 int vim_regexec_prog(regprog_T **prog, int ignore_case, char_u *line, colnr_T col);
 int vim_regexec(regmatch_T *rmp, char_u *line, colnr_T col);
 int vim_regexec_nl(regmatch_T *rmp, char_u *line, colnr_T col);
-long vim_regexec_multi(regmmatch_T *rmp, win_T *win, buf_T *buf, linenr_T lnum, colnr_T col, proftime_T *tm);
+long vim_regexec_multi(regmmatch_T *rmp, win_T *win, buf_T *buf, linenr_T lnum, colnr_T col, proftime_T *tm, int *timed_out);
 /* vim: set ft=c : */