Add friend header to each type for separate compilation

Author: mborland

include/boost/decimal/decimal128.hpp

@@ -37,6 +37,7 @@
 #include <boost/decimal/detail/sub_impl.hpp>
 #include <boost/decimal/detail/mul_impl.hpp>
 #include <boost/decimal/detail/div_impl.hpp>
+#include <boost/decimal/detail/cmath/next.hpp>
 
 #ifndef BOOST_DECIMAL_BUILD_MODULE
 

include/boost/decimal/decimal128_fast.hpp

@@ -17,6 +17,7 @@
 #include <boost/decimal/detail/div_impl.hpp>
 #include <boost/decimal/detail/emulated128.hpp>
 #include <boost/decimal/detail/ryu/ryu_generic_128.hpp>
+#include <boost/decimal/detail/cmath/next.hpp>
 
 #ifndef BOOST_DECIMAL_BUILD_MODULE
 

include/boost/decimal/decimal32_fast.hpp

@@ -17,6 +17,7 @@
 #include <boost/decimal/detail/ryu/ryu_generic_128.hpp>
 #include <boost/decimal/detail/promotion.hpp>
 #include <boost/decimal/detail/comparison.hpp>
+#include <boost/decimal/detail/cmath/next.hpp>
 
 #ifndef BOOST_DECIMAL_BUILD_MODULE
 #include <limits>

include/boost/decimal/decimal64.hpp

@@ -40,6 +40,7 @@
 #include <boost/decimal/detail/div_impl.hpp>
 #include <boost/decimal/detail/promote_significand.hpp>
 #include <boost/decimal/detail/components.hpp>
+#include <boost/decimal/detail/cmath/next.hpp>
 
 #ifndef BOOST_DECIMAL_BUILD_MODULE
 

include/boost/decimal/decimal64_fast.hpp

@@ -18,6 +18,7 @@
 #include <boost/decimal/detail/promote_significand.hpp>
 #include <boost/decimal/detail/ryu/ryu_generic_128.hpp>
 #include <boost/decimal/detail/promotion.hpp>
+#include <boost/decimal/detail/cmath/next.hpp>
 
 #ifndef BOOST_DECIMAL_BUILD_MODULE