wined3d: Rename renderUpsideDown to render_offscreen.

dlls/wined3d/wined3d_private.h

diff --git a/dlls/wined3d/wined3d_private.h b/dlls/wined3d/wined3d_private.h
index 1d8bb10..aa38261 100644
--- a/dlls/wined3d/wined3d_private.h
+++ b/dlls/wined3d/wined3d_private.h
@@ -545,7 +545,7 @@
     UINT                    currentPalette;
 
     /* For rendering to a texture using glCopyTexImage */
-    BOOL                    renderUpsideDown;
+    BOOL                    render_offscreen;
 
     /* Cursor management */
     BOOL                    bCursorVisible;