missing include (clang compatibility)

[Ralf W. Grosse-Kunstleve]

% diff boost/math/special_functions/detail/bessel_jy.hpp boost/math/special_functions/detail/bessel_jy_.hpp 19a20

#include <boost/math/special_functions/detail/bessel_jy_series.hpp>

GCC seems fine with/without the include. Here is the clang error without the include:

boost/boost/math/special_functions/detail/bessel_jy.hpp:363:16: error:

call to function 'bessel_yn_small_z' that is neither visible in the template definition nor found by argument-dependent lookup

Yv = bessel_yn_small_z(n, x, &Yv_scale, pol);

boost/boost/math/special_functions/detail/bessel_jy_series.hpp:213:3: note:

'bessel_yn_small_z' should be declared prior to the call site or in namespace 'boost::math::policies'

T bessel_yn_small_z(int n, T z, T* scale, const Policy& pol)

[John Maddock]

(In [74937]) Add missing #include. Fixes #6017.