Updated PeterG's internals documentation per comments from

Monty; new description of /man subdirectory

Docs/internals.texi

@@ -3774,8 +3774,10 @@ lib_vio.c --  Emulate the vio directory's communication buffer
 Some user-contributed manual pages
 @*@*
 
-These are not the actual "man" (manual) pages, they are switches for
-the production.
+These are user-contributed "man" (manual) pages in a special markup 
+format. The format is described in a document with a heading like
+"man page for man" or "macros to format man pages" which you can find 
+in a Linux directory or on the Internet.
 @*@*
 
 @subsection myisam