Minor vertex array support tweaks. Most of these are in preparation for the

Minor vertex array support tweaks.  Most of these are in preparation for the
(eventual) addition of support for ARB_vertex_buffer_object.

Move all the private vertex array data structures out of
indirect_vertex_array.c and into indirect_va_private.h.

Rename array_state_vector::enabled_array_count to
array_state_vector::enabled_client_array_count.

Make sure that both the GL extension string and the server GL version are
available when __glXInitVertexState is called.

Make sure that array_state::normalized is set correctly in the array's
gl*Pointer function.