mesa: Put materials at the end of the generic block.

mesa: Put materials at the end of the generic block.

The materials are now moved to the end of the
generic attributes block to the range 4-15.

Before, the way the position and generic 0 attribute
is handled was dependent on the presence and kind of
the currently attached vertex program. With this
change the way the position attribute and the generic 0
attribute is treated only depends on the enabled
flag of those two arrays.
This will later help to untangle the update dependencies
between enabled arrays and shader inputs.

v2: s,VERT_ATTRIB_MAT_OFFSET,VERT_ATTRIB_MAT0,g

Signed-off-by: Mathias Fröhlich <Mathias.Froehlich@web.de>
Reviewed-by: Brian Paul <brianp@vmware.com>