patch 9.0.1774: no support for custom cmdline completion

Problem:  no support for custom cmdline completion
Solution: Add new vimscript functions

Add the following two functions:
- getcmdcompltype() returns custom and customlist functions

- getcompletion() supports both custom and customlist

closes: #12228

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Shougo Matsushita <Shougo.Matsu@gmail.com>
diff --git a/src/version.c b/src/version.c
index ffecee9..dbe15f8 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1774,
+/**/
     1773,
 /**/
     1772,