patch 8.2.1166: once mouse move events are enabled getchar() returns them

Problem:    Once mouse move events are enabled getchar() returns them.
Solution:   Ignore K_MOUSEMOVE in getchar(). (closes #6424)
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 10b57b7..08399b8 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -5023,8 +5023,9 @@
 		When the user clicks a mouse button, the mouse event will be
 		returned.  The position can then be found in |v:mouse_col|,
 		|v:mouse_lnum|, |v:mouse_winid| and |v:mouse_win|.
-		|getmousepos()| can also be used.  This example positions the
-		mouse as it would normally happen: >
+		|getmousepos()| can also be used.  Mouse move events will be
+		ignored.
+		This example positions the mouse as it would normally happen: >
 			let c = getchar()
 			if c == "\<LeftMouse>" && v:mouse_win > 0
 			  exe v:mouse_win . "wincmd w"