wined3d: Get rid of struct glDescriptor.

In general it might not be a bad idea to group GL specific data into a
separate struct, but IWineD3DSurfaceImpl is currently the only thing that
bothers. It doesn't get it quite right either, since e.g. the PBO isn't in
glDescriptor either.
diff --git a/dlls/wined3d/wined3d_private.h b/dlls/wined3d/wined3d_private.h
index d8c56e7..b80c35c 100644
--- a/dlls/wined3d/wined3d_private.h
+++ b/dlls/wined3d/wined3d_private.h
@@ -1924,14 +1924,16 @@
 
     /* PBO */
     GLuint                    pbo;
+    GLuint texture_name;
+    GLuint texture_name_srgb;
+    GLint texture_level;
+    GLenum texture_target;
 
     RECT                      lockedRect;
     RECT                      dirtyRect;
     int                       lockCount;
 #define MAXLOCKCOUNT          50 /* After this amount of locks do not free the sysmem copy */
 
-    glDescriptor              glDescription;
-
     /* For GetDC */
     wineD3DSurface_DIB        dib;
     HDC                       hDC;