#include <unistd.h> is only included if not on WIN32 (which does not have unistd.h)
finished implementation of sensitivity propagation techniques for ERK methods
Merge branch 'stable' of github.com:tibnor/acado into tibnor-stable
improved speed of ERK methods forward sensitivity propagation
added AD support for forward and backward derivatives with matrix seeds
improved forward sensitivity propagation in ERK methods using the new AD functionality
improved forward-over-backward second order sensitivity propagation in ERK methods using the new AD functionality
added custom functionionality for the new three-sweeps-propagation approach to make it at least competitive with forward-over-backward, currently lacking specific AD functionality for the operators involved
added symmetric AD functionality, fixed ADbackward, enabled stacking of variables
Merge branch 'master' of github.com:rienq/acado into stable

Conflicts:
	examples/basic_data_structures/function/symbolic_differentiation3.cpp
	external_packages/src/acado_gnuplot/gnuplot_window.cpp
	include/acado/utils/acado_types.hpp
	src/symbolic_operator/projection.cpp
resolved merge conflicts
modified function.cpp