Reorder l3msg documentation to emphasize customizable aspects (fixes #…

…887)

l3kernel/l3msg.dtx

@@ -125,6 +125,40 @@
 %   defined.
 % \end{function}
 %
+% \section{Customizable information for message modules}
+%
+% \begin{function}[EXP, added = 2018-10-10]{\msg_module_name:n}
+%   \begin{syntax}
+%     \cs{msg_module_name:n} \Arg{module}
+%   \end{syntax}
+%   Expands to the public name of the \meta{module} as defined by
+%   \cs{g_msg_module_name_prop} (or otherwise leaves the \meta{module}
+%   unchanged).
+% \end{function}
+%
+% \begin{function}[EXP, added = 2018-10-10]{\msg_module_type:n}
+%   \begin{syntax}
+%     \cs{msg_module_type:n} \Arg{module}
+%   \end{syntax}
+%   Expands to the description which applies to the \meta{module},
+%   for example a |Package| or |Class|. The information here is defined
+%   in \cs{g_msg_module_type_prop}, and will default to |Package| if an
+%   entry is not present.
+% \end{function}
+%
+% \begin{variable}[added = 2018-10-10]{\g_msg_module_name_prop}
+%   Provides a mapping between the module name used for messages, and that
+%   for documentation. For example, \LaTeX{}3 core messages are stored in
+%   the reserved |LaTeX| tree, but are printed as |LaTeX3|.
+% \end{variable}
+%
+% \begin{variable}[added = 2018-10-10]{\g_msg_module_type_prop}
+%   Provides a mapping between the module name used for messages, and that
+%   type of module. For example, for \LaTeX{}3 core messages, an empty entry
+%   is set here meaning that they are not described using the standard
+%   |Package| text.
+% \end{variable}
+%
 % \section{Contextual information for messages}
 %
 % \begin{function}[rEXP]{\msg_line_context:}
@@ -215,25 +249,6 @@
 %   |Package| is the standard outcome: see \cs{msg_module_type:n}.
 % \end{function}
 %
-% \begin{function}[EXP, added = 2018-10-10]{\msg_module_name:n}
-%   \begin{syntax}
-%     \cs{msg_module_name:n} \Arg{module}
-%   \end{syntax}
-%   Expands to the public name of the \meta{module} as defined by
-%   \cs{g_msg_module_name_prop} (or otherwise leaves the \meta{module}
-%   unchanged).
-% \end{function}
-%
-% \begin{function}[EXP, added = 2018-10-10]{\msg_module_type:n}
-%   \begin{syntax}
-%     \cs{msg_module_type:n} \Arg{module}
-%   \end{syntax}
-%   Expands to the description which applies to the \meta{module},
-%   for example a |Package| or |Class|. The information here is defined
-%   in \cs{g_msg_module_type_prop}, and will default to |Package| if an
-%   entry is not present.
-% \end{function}
-%
 % \begin{function}[EXP,updated = 2018-09-30]{\msg_see_documentation_text:n}
 %   \begin{syntax}
 %     \cs{msg_see_documentation_text:n} \Arg{module}
@@ -246,23 +261,10 @@
 %   \end{quote}
 %   This function can be redefined to alter the language in which the
 %   message is given, using |#1| as the name of the \meta{module} to
-%   be included. The name of the \meta{module} may be altered by use of
-%   \cs{g_msg_module_documentation_prop}
+%   be included.  The name of the \meta{module} is produced using
+%   \cs{msg_module_name:n}.
 % \end{function}
 %
-% \begin{variable}[added = 2018-10-10]{\g_msg_module_name_prop}
-%   Provides a mapping between the module name used for messages, and that
-%   for documentation. For example, \LaTeX{}3 core messages are stored in
-%   the reserved |LaTeX| tree, but are printed as |LaTeX3|.
-% \end{variable}
-%
-% \begin{variable}[added = 2018-10-10]{\g_msg_module_type_prop}
-%   Provides a mapping between the module name used for messages, and that
-%   type of module. For example, for \LaTeX{}3 core messages, an empty entry
-%   is set here meaning that they are not described using the standard
-%   |Package| text.
-% \end{variable}
-%
 % \section{Issuing messages}
 %
 % Messages behave differently depending on the message class. In all cases,