Add patch from issue

include/boost/math/policies/error_handling.hpp

@@ -26,9 +26,9 @@
 #include <complex>
 #include <cstdint>
 #include <cstring>
+#ifndef BOOST_MATH_NO_EXCEPTIONS
 #include <iomanip>
 #include <sstream>
-#ifndef BOOST_MATH_NO_EXCEPTIONS
 #include <stdexcept>
 #endif
 #include <string>
@@ -95,6 +95,8 @@ T user_indeterminate_result_error(const char* function, const char* message, con
 namespace detail
 {
 
+#ifndef BOOST_MATH_NO_EXCEPTIONS
+// Only used to build exception messages; relies on <sstream>
 template <class T>
 inline std::string prec_format(const T& val)
 {
@@ -124,7 +126,9 @@ inline std::string prec_format<std::float128_t>(const std::float128_t& val)
    return std::string(buffer, r.ptr);
 }
 
-#endif
+#endif // BOOST_MATH_USE_CHARCONV_FOR_CONVERSION
+
+#endif // BOOST_MATH_NO_EXCEPTIONS
 
 inline void replace_all_in_string(std::string& result, const char* what, const char* with)
 {