Since Ceres is moving to using GitHub for issues, and the Google
Code URL in the current copyright header will soon become invalid,
update all the headers.
Change-Id: I1fce70375d1bcf098591f07b4d8f01a5c1e0789c
1. Base class for preprocessors.
2. A preprocessor for problems that will be solved using
the trust region minimizer.
3. Added sanity tests to the program reordering options
for Schur type linear solvers.
4. Tests for the TrustRegionPreprocessor.
Change-Id: I88cd926f0053bbbf2bd6b11e03ec55b8bf473cf1