solver-callbacks: fixing warning, comment and inclusion guard.
Update curvature example.
New example: confidence interval.
Update VC version check for generic lambdas.
Allow more constrained iterations.
New Catch version.
Experimental support for sym-ildl (if available).
Add tests for sym-ildl. (disabled by default).
Always print H_ii.
Remove unused code.
Bug fix sym-ildl: permutation matrix inverse.
Use the same type of block diagonal modification for sym-ildl.
Enable testing of sym-ildl.
sym-ildl passes NIST test suite.