replace TAILQ_EMPTY/INSERT_HEAD/TAIL dance with a single TAILQ_INSERT_TAIL Now that all the queues are correctly initialised, there's no need for that dance.

initialize all the queues

rendering text/plain documents as text an not pre-content let's start an experiments: using LINE_TEXT instead of LINE_PRE_CONTENT for documents managed by the texplain parser. I never read much text/plain content until now, but by starting to use finger and gopher the amount of text pages is only bound to grow.

factorize the line type

rename textplain/gemtext.c to parser_*