mesa: add gl_texture_image::Face, Level fields

Several drivers have these fields in their subclasses of gl_texture_image.
They'll be useful for core Mesa too...

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/mesa/main/mtypes.h

@@ -1279,6 +1279,9 @@ struct gl_texture_image
    GLboolean _IsPowerOfTwo;	/**< Are all dimensions powers of two? */
 
    struct gl_texture_object *TexObject;  /**< Pointer back to parent object */
+   GLuint Level;                /**< Which mipmap level am I? */
+   /** Cube map face: index into gl_texture_object::Image[] array */
+   GLuint Face;
 
    FetchTexelFuncC FetchTexelc;	/**< GLchan texel fetch function pointer */
    FetchTexelFuncF FetchTexelf;	/**< Float texel fetch function pointer */

src/mesa/main/teximage.c

@@ -571,6 +571,8 @@ _mesa_set_tex_image(struct gl_texture_object *tObj,
 
    /* Set the 'back' pointer */
    texImage->TexObject = tObj;
+   texImage->Level = level;
+   texImage->Face = face;
 }