patch 9.0.1916: Crash when allocating large terminal screen

Problem:  Crash when allocating large terminal screen
Solution: Don't allow values > 1000 for terminal
          screen columns and rows

closes: #13126

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/visual.txt b/runtime/doc/visual.txt
index 616e773..a91969e 100644
--- a/runtime/doc/visual.txt
+++ b/runtime/doc/visual.txt
@@ -183,7 +183,7 @@
 CTRL-C			In Visual mode: Stop Visual mode.  When insert mode is
 			pending (the mode message shows
 			"-- (insert) VISUAL --"), it is also stopped.
-			On MS-Windows, you may need to press CTRL-Break 
+			On MS-Windows, you may need to press CTRL-Break
 			|dos-CTRL-Break|.
 
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