The ABM stepper was missing reset functionality, see #182

addressing #184, simple fix is to also reset m_current_k_opt and therefore
make sure the loop doesnt overshoot.

Performance improvement for Bulirsch-Stoer-Stepper

Becoming suspicious by the difference of the exponents used for computing the
new step size in the BS and BS denseout stepper (see
0f943fb) I checked again the Hairer book and
I'm now convinced there was a mistake in our implementation and both
steppers should use 1/(2*k+1) as exponent. The background is the this exponent
represents the order of the error of the k-th iteration, and this order is
always 2k+1, independent of the interval_sequence. This error is computed from
the difference of the k-th and k-1 - th iteration, which have the orders 2k+2
2k respectively, which means the computed error has order 2k+1.

A bug introduced with the recent max_dt facility prevented the rosenbrock
controller to increase step size in most cases (if max_dt=0). This is fixed
now, and a regression test case has been added.

Remove .gitmodules

update for ticket #12034

Fix failed two tests.

Fix unused variable warning

This adds the flag -Wno-unused-local-typedef to the global build
options on Jenkins to shorten the log file for the clang build
when building Boost.

Merge from headmyshoulder/odeint-v2