used by those algorithms (aka "second level").
This is a row import : we copy/paste the files from cminpack and make
very few changes :
* template<Scalar> them (replace double)
* dpmpar() replaced by c++ standard equivalent
* abs/fabs/sqrt/min/max replaced by ei_* or std::*
* use eigen norms instead of enorm()
Important Notes:
* The use of stableNorm() was not enough in some cases, but using
blueNorm() instead fixed the problems (some tests gave bad results,
either in number of iterations or precision of the results)
* As a whole, the only test that changed is testNistMGH17() : it now takes
some few steps less to get the same result. So this is a small improvement.
After this commit, the only remaining dependency from the cminpack
static library is 'covar', only used from the tests.
