patch 9.1.1505: not possible to return completion type for :ex command

Problem:  not possible to return command-line completion type for :ex
          command
Solution: make getcmdcompltype() accept an optional and return the
          command-line completion for that arg (Shougo Matsushita).

closes: #17606

Signed-off-by: Shougo Matsushita <Shougo.Matsu@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/evalfunc.c b/src/evalfunc.c
index a31ad13..6ba698d 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -2264,7 +2264,7 @@
 			ret_string,	    f_getcharstr},
     {"getcmdcomplpat",	0, 0, 0,	    NULL,
 			ret_string,	    f_getcmdcomplpat},
-    {"getcmdcompltype",	0, 0, 0,	    NULL,
+    {"getcmdcompltype",	0, 1, FEARG_1,	    NULL,
 			ret_string,	    f_getcmdcompltype},
     {"getcmdline",	0, 0, 0,	    NULL,
 			ret_string,	    f_getcmdline},