Backport 1.3 documenting impending deprecation in favor of the email

module.

Doc/lib/libmimewriter.tex

@@ -6,6 +6,11 @@
 \modulesynopsis{Generic MIME file writer.}
 \sectionauthor{Christopher G. Petrilli}{petrilli@amber.org}
 
+\deprecated{2.3}{The \refmodule{email} package should be used in
+                 preference to the \module{MimeWriter} module.  This
+                 module is present only to maintain backward
+                 compatibility.}
+
 This module defines the class \class{MimeWriter}.  The
 \class{MimeWriter} class implements a basic formatter for creating
 MIME multi-part files.  It doesn't seek around the output file nor