Add C hooks and prototypes for wiki-markup tags.
emit_style_tag, parse_italics, parse_bold
parse_italics_and_bold() and parse_style()
handle_list_marker() and handle_list()
handle_hr()
handle_dl_term()
Add a emit_string() as a shortcut; a bunch of minor cleanup.
To clarify usage, emit_text() -> emit_char() and emit_string() -> emit_text()