Two bug corrections and one new feature.

Two bug corrections and one new feature.

(Ada_funcs): Do not tag "use type Xxxx;".

New language HTML.
(make_tag): Never generate null length tag names.
(linebuffer_init): Renamed from initbuffer.  All callers changed.
(pattern): Structure renamed to `regexp', member regex renamed to
pattern.
(node_st): Member pat renamed to regex.
(pattern); New member force_explicit_name, for future use.  Now
always set to true, cannot be reset.
(add_regex, regex_tag_multiline, readline): Use it.
(main): Free some global structures.

(fdesc): New member `written'.
(readline, process_file): Initialise it.
(put_entries): Set it.
(main): Use it to create entries for files without tags.
(total_size_of_entries): Do not count invalid tags.
(etags_strcasecmp): Like BSD's, for compatibility.
(strcaseeq): Make it into a macro.