* Change eigen algebra to support Eigen>=3.3
An internal change in Eigen made odeint incompatible with Eigen
versions >=3.3. This commit changes odeint in such a way that it
does not rely on the changed behvior, so it is now compatible with
old and new Eigen.
Fixes#194
* Remove obsolete Eigen fail compile test
* Remove compile-fail test for C++98 unwrap_reference
generate function now support additional max_dt parameter for setting the set
size limit.
Added a test case to check limiter behavior for controlled and dense out
integration.
Following the discussion in #173, the integrate_const function now
provide a mechanisms to check for TOO_MUCH_WORK situations where too
many steps are performed without any progress (i.e. observer calls).
Naturally, this only makes sense for controlled steppers or dense
output steppers.
Also, integrate_adaptive functions do not require such functionality as
there observer calls happen at every time step.
Hence, only integrate_n_steps and integrate_times will be adapted shortly
when state_type == time_type (e.g. 1d odes with state_type = double), some
do_step overloads are disabled due to ambiguities of parameter structure.
However, the initialization of the Adams-Bashforth needs some of those
disabled functions in its initialization. As a fix, I added do_step_dxdt to
the stepper base classes to provide direct access to the required functions
that will not be disabled in the case of state_type == time_type.
