wined3d: Add pow2Matrix_identity flag to BaseTextureClass struct.

New flag helps to quickly find out whether the pow2Matrix is a
identity matrix (no texcoord fixup needed) or not.
diff --git a/dlls/wined3d/wined3d_private.h b/dlls/wined3d/wined3d_private.h
index fdd28da..abab9dc 100644
--- a/dlls/wined3d/wined3d_private.h
+++ b/dlls/wined3d/wined3d_private.h
@@ -1384,6 +1384,7 @@
     LONG                    bindCount;
     DWORD                   sampler;
     BOOL                    is_srgb;
+    BOOL                    pow2Matrix_identity;
     const struct min_lookup *minMipLookup;
     const GLenum            *magLookup;
     void                    (*internal_preload)(IWineD3DBaseTexture *iface, enum WINED3DSRGB srgb);