NewtonSolver: Check for result of linear solve

new DiffSolver result for error in linear solve, flag for disabling the check
DenseMatrix::evd() patch from David Knezevic.

This patch is from June 2011, it unfortunately got lost in my email
around that time.  Its functionality is now more readily-available
from Eigen, but I think it could still be useful in some situations.
Pass DenseVector storage directly to Lapack.
Merge branch 'dense_evd'

I compared eigenvalues computed with the new method to Octave for some
random test matrices and the results agreed.
Fix unused variable warning.
Fixing scalable_allocator declaration.
Merge pull request #295 from libMesh/valgrind_tbb

Fixing scalable_allocator declaration.
Read 0-dimensional elements (points) in Gmsh files

Add them to the BoundaryInfo object with the correct boundary_id.
Merge pull request #296 from libMesh/gmsh

Read 0-dimensional elements (points) in Gmsh files
update Makefile.orig and add instructions to rebuild fpoptimizer.cc
all_first_order() only works if renumbering is allowed.
Merge pull request #298 from libMesh/debug_adaptivity_ex3

all_first_order() only works if renumbering is allowed.
Default track_linear_convergence to false.
Use libmesh indentation levels.
Merge branch 'check-linear-solver'

This is Robert W's branch with a different default value for
track_linear_convergence.
Use the LIBMESH_DIR environment variable, if it exists, to find a
valid libmesh installation.
Miscellaneous fixes to new README file:

* Fix typo.
* Use 'rm -f' for .dep and fpoptimizer.cc
* List known limitations on the process of rebuilding fpoptimizer.cc
Merge branch 'fpoptimizer'

Branch from Daniel Schwen with a few improvements for finding the
appropriate LIBMESH_DIR.
Print slepc version number during configure summary.
Add lines of code count for 4 July 2014.