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/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index 123dcbb..af67429 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -1068,6 +1068,8 @@
 	swapname()		get the swap file path of a buffer
 
 Command line:					*command-line-functions*
+	getcmdcomplpat()	get completion pattern of the current command
+				line
 	getcmdcompltype()	get the type of the current command line
 				completion
 	getcmdline()		get the current command line input