* BOOST_MATH_EXPORT on the public declarations in math_fwd.hpp,
round_fwd.hpp, unchecked_factorial.hpp, unchecked_bernoulli.hpp and
every special function header (declaration and definition sites)
* Adds special_functions.hpp to the module interface unit
* rsqrt.hpp, jacobi.hpp and cardinal_b_spline.hpp now include
tools/config.hpp so the export macro is always defined
* math_unit_test.hpp resolves math entities through the import in
module mode
* Module test harness gains test_digamma_simple, test_expm1_simple,
test_log1p_simple, git_issue_1194 and git_issue_1255
Matt Borland