patch 9.1.0770: current command line completion is a bit limited

Problem:  current command completion is a bit limited
Solution: Add the shellcmdline completion type and getmdcomplpat()
          function (Ruslan Russkikh).

closes: #15823

Signed-off-by: Ruslan Russkikh <dvrussk@yandex.ru>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/proto/ex_getln.pro b/src/proto/ex_getln.pro
index 1ab3b1c..cc8723a 100644
--- a/src/proto/ex_getln.pro
+++ b/src/proto/ex_getln.pro
@@ -30,6 +30,7 @@
 void escape_fname(char_u **pp);
 void tilde_replace(char_u *orig_pat, int num_files, char_u **files);
 cmdline_info_T *get_cmdline_info(void);
+void f_getcmdcomplpat(typval_T *argvars, typval_T *rettv);
 void f_getcmdcompltype(typval_T *argvars, typval_T *rettv);
 void f_getcmdline(typval_T *argvars, typval_T *rettv);
 void f_getcmdpos(typval_T *argvars, typval_T *rettv);