general identifiers for which closing tags will be omitted
when SGML is generated. This can be used to tell the markup
generator to drop stuff like </para>. Note that it needs to
be possible for the closing tag to *always* be omitted for it
to be included in "autoclose".
main(): Added command-line option "-a" / "--autoclose" to set the
list of general identifiers passed to the convert() function
as the "autoclose" parameter. The list may only be specified
once (not additive) and GIs should be comma-separated. The
default list includes only "para".