patch 8.2.2963: GUI: mouse move may start Visual mode with a popup visible

Problem:    GUI: mouse move may start Visual mode with a popup visible.
Solution:   Add special code for mouse move. (closes #8318)
diff --git a/src/vim.h b/src/vim.h
index 10f032f..61afe97 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1859,6 +1859,8 @@
 #define MOUSE_6	0x500	// scroll wheel left
 #define MOUSE_7	0x600	// scroll wheel right
 
+#define MOUSE_MOVE 0x700    // report mouse moved
+
 // 0x20 is reserved by xterm
 #define MOUSE_DRAG_XTERM   0x40