LWG4440 Forward declarations of entities need also in entries

Fixes US 65-116 (C++26 CD).

Author: burblebee

source/support.tex

@@ -608,7 +608,7 @@
 #define @\defnlibxname{cpp_lib_byte}@                              201603L // freestanding, also in \libheader{cstddef}
 #define @\defnlibxname{cpp_lib_byteswap}@                          202110L // freestanding, also in \libheader{bit}
 #define @\defnlibxname{cpp_lib_char8_t}@                           201907L
-  // freestanding, also in \libheader{atomic}, \libheader{filesystem}, \libheader{istream}, \libheader{limits}, \libheader{locale}, \libheader{ostream}, \libheader{string},
+  // freestanding, also in \libheader{atomic}, \libheader{filesystem}, \libheader{iosfwd}, \libheader{istream}, \libheader{limits}, \libheader{locale}, \libheader{ostream}, \libheader{string},
   // \libheader{string_view}
 #define @\defnlibxname{cpp_lib_chrono}@                            202306L // also in \libheader{chrono}
 #define @\defnlibxname{cpp_lib_chrono_udls}@                       201304L // also in \libheader{chrono}
@@ -835,7 +835,7 @@
 #define @\defnlibxname{cpp_lib_source_location}@                   201907L // freestanding, also in \libheader{source_location}
 #define @\defnlibxname{cpp_lib_span}@                              202311L // freestanding, also in \libheader{span}
 #define @\defnlibxname{cpp_lib_span_initializer_list}@             202311L // freestanding, also in \libheader{span}
-#define @\defnlibxname{cpp_lib_spanstream}@                        202106L // also in \libheader{spanstream}
+#define @\defnlibxname{cpp_lib_spanstream}@                        202106L // also in \libheader{iosfwd}, \libheader{spanstream}
 #define @\defnlibxname{cpp_lib_ssize}@                             201902L // freestanding, also in \libheader{iterator}
 #define @\defnlibxname{cpp_lib_sstream_from_string_view}@          202306L // also in \libheader{sstream}
 #define @\defnlibxname{cpp_lib_stacktrace}@                        202011L // also in \libheader{stacktrace}
@@ -848,7 +848,7 @@
 #define @\defnlibxname{cpp_lib_string_udls}@                       201304L // also in \libheader{string}
 #define @\defnlibxname{cpp_lib_string_view}@                       202403L // also in \libheader{string}, \libheader{string_view}
 #define @\defnlibxname{cpp_lib_submdspan}@                         202411L // freestanding, also in \libheader{mdspan}
-#define @\defnlibxname{cpp_lib_syncbuf}@                           201803L // also in \libheader{syncstream}
+#define @\defnlibxname{cpp_lib_syncbuf}@                           201803L // also in \libheader{iosfwd}, \libheader{syncstream}
 #define @\defnlibxname{cpp_lib_task}@                              202506L // also in \libheader{execution}
 #define @\defnlibxname{cpp_lib_text_encoding}@                     202306L // also in \libheader{text_encoding}
 #define @\defnlibxname{cpp_lib_three_way_comparison}@              201907L // freestanding, also in \libheader{compare}