This involves reworking the blocktag[] array into a STRING(), and moving the entire
kit and kaboodle out into a separate file with a public initializer (mkd_prepare_tags),
definer (mkd_define_tag) sort (mkd_sort_tags, and lookup (mkd_search_tags) function.
The html5 tags are further removed into their own function (mkd_with_html5_tags) which
can be included when someone wishes to have html5 support.
Note that html5 support is library-wide; once you call mkd_with_html5_tags, you're
stuck with them everywhere and can't back them out. This might be revisited later,
