patch 9.0.2025: no cmdline completion for ++opt args

Problem:  no cmdline completion for ++opt args
Solution: Add cmdline completion for :e ++opt=arg and :terminal
          [++options]

closes: #13319

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Yee Cheng Chin <ychin.git@gmail.com>
diff --git a/src/proto/ex_docmd.pro b/src/proto/ex_docmd.pro
index 3a1dc5f..3fd20b2 100644
--- a/src/proto/ex_docmd.pro
+++ b/src/proto/ex_docmd.pro
@@ -30,6 +30,7 @@
 void separate_nextcmd(exarg_T *eap, int keep_backslash);
 char_u *skip_cmd_arg(char_u *p, int rembs);
 int get_bad_opt(char_u *p, exarg_T *eap);
+int expand_argopt(char_u *pat, expand_T *xp, regmatch_T *rmp, char_u ***matches, int *numMatches);
 int ends_excmd(int c);
 int ends_excmd2(char_u *cmd_start, char_u *cmd);
 char_u *find_nextcmd(char_u *p);