patch 9.1.0509: not possible to translate Vim script messages

Problem:  not possible to translate Vim script messages
          (RestorerZ)
Solution: implement bindtextdomain() and gettext() to support Vim script
          message translations (Christ van Willegen)

fixes: #11637
closes: #12447

Signed-off-by: Christ van Willegen <cvwillegen@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/version9.txt b/runtime/doc/version9.txt
index d50e0e8..b60f386 100644
--- a/runtime/doc/version9.txt
+++ b/runtime/doc/version9.txt
@@ -41563,6 +41563,9 @@
 Support highlighting the matched text for insert-mode completion and
 command-line completion in |ins-completion-menu|.
 
+Support for translating messages in Vim script plugins using the |gettext()|
+and |bindtextdomain()| functions.
+
 							*changed-9.2*
 Changed~
 -------
@@ -41579,6 +41582,7 @@
 
 Functions: ~
 
+|bindtextdomain()|	set message lookup translation base path
 |diff()|		diff two Lists of strings
 |filecopy()|		copy a file {from} to {to}
 |foreach()|		apply function to List items