gty.texi (Options): Document the mark_hook option to GTY.

gty.texi (Options): Document the mark_hook option to GTY.

2007-01-19  Basile Starynkevitch  <basile@starynkevitch.net>

	* gcc/doc/gty.texi (Options): Document the mark_hook option to
	GTY.
	* gcc/gengtype.c (write_types_data, write_func_for_structure,
	write_types, ggc_wtd, pch_wtd): Added skip_hooks to
	write_types_data, ggc_wtd, pch_wtd for mark_hook.
	(walk_type, write_func_for_structure): Generate the mark_hook if
	needed.

	* MAINTAINERS: added myself (Basile Starynkevitch) to write after
	approval.

From-SVN: r120973