Disable xdr when we don't support xdr

This should fix a regression in the BuildBot Barebones tests
AdjointRefinement fixes

In the general case, we only need to compute requested adjoints, not
every adjoint.

In the heterogeneous BCs case, we may need to subtract off the coarse
grid lift function rather than the fine grid lift.
Fixes for Xdr I/O with varying id sizes
Merge pull request #176 from libMesh/xdr_type_fixes

Fixes for Xdr I/O with varying id sizes
Merge pull request #166 from libMesh/intro_ex1_fix

Disable xdr when we don't support xdr
Merge pull request #173 from libMesh/adjoint_refinement_lift

AdjointRefinement fixes
#include <sstream> for solaris studio
Adding second derivatives for Hex20.

Maple script used for computing the derivatives:
https://gist.github.com/jwpeterson/7555673
- Updated assignment operator in BoundaryInfo to copy over edge data.
- Updated MeshTools::Modification::change_boundary_id to modify edge and node boundary data.
- Updated SerialMesh::stitching_helper to copy over edge and node boundary data.