fix: add GTSAM_USE_BOOST_FEATURES to definitions

[ArkadiuszNiemiec]

This fixes the issue #1994 and some issues mentioned in #1967 and #1981.

The change defines the proper identifier if GTSAM_USE_BOOST_FEATURES option is set in CMakeLists.txt.
It's used in:

gtsam/gtsam/base/concepts.h

Lines 11 to 24 in 7b56d66

	#if GTSAM_USE_BOOST_FEATURES
	#include <boost/concept_check.hpp>
	#include <boost/concept/assert.hpp>
	#include <boost/concept/requires.hpp>
	#include <boost/concept_check.hpp>
	#define GTSAM_CONCEPT_ASSERT(concept) BOOST_CONCEPT_ASSERT((concept))
	#define GTSAM_CONCEPT_REQUIRES(concept, return_type) BOOST_CONCEPT_REQUIRES(((concept)), (return_type))
	#else
	// This does something sensible:
	#define BOOST_CONCEPT_USAGE(concept) void check##concept()
	// These just ignore the concept checking for now:
	#define GTSAM_CONCEPT_ASSERT(concept) static_assert(true, "")
	#define GTSAM_CONCEPT_REQUIRES(concept, return_type) return_type
	#endif

...and without it the compiler throws BOOST_CONCEPT_USAGE redefinition error.