Explicitly delete all non implemented assignment operators.

Commit (almost) automatically generated with the following sed command:
sed -i -ne '1h;1!H;${g;s|\n[[:blank:]]*private:\n\([[:blank:]]*\)// silence MSVC warning C4512: assignment operator could not be generated\n\([[:blank:]]*\)\([^\n]\+\);\n|\n\1// silence MSVC warning C4512: assignment operator could not be generated\n\2BOOST_DELETED_FUNCTION(\3)\n|g;p}' $(git ls-files)

include/boost/fusion/sequence/io/detail/manip.hpp

@@ -144,9 +144,8 @@ namespace boost { namespace fusion
 
             Stream& stream;
 
-        private:
             // silence MSVC warning C4512: assignment operator could not be generated
-            string_ios_manip& operator= (string_ios_manip const&);
+            BOOST_DELETED_FUNCTION(string_ios_manip& operator= (string_ios_manip const&))
         };
 
     } // detail