Rearrange Elem members to reduce struct padding
Rearrange Elem members to reduce struct padding

On 64-bit machines when configuring with 32-bit subdomain ids this
ought to save us 8 bytes per Elem.

Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh