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/evalfunc.c b/src/evalfunc.c
index 67104ea..d902045 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -2091,6 +2091,8 @@
 			ret_dict_any,	    f_getcharsearch},
     {"getcharstr",	0, 1, 0,	    arg1_bool,
 			ret_string,	    f_getcharstr},
+    {"getcmdcomplpat",	0, 0, 0,	    NULL,
+			ret_string,	    f_getcmdcomplpat},
     {"getcmdcompltype",	0, 0, 0,	    NULL,
 			ret_string,	    f_getcmdcompltype},
     {"getcmdline",	0, 0, 0,	    NULL,