langhooks.h (struct lang_hooks): Document that tree_size langhook may be also called on tcc_type nodes.

	* langhooks.h (struct lang_hooks): Document that tree_size langhook
	may be also called on tcc_type nodes.
	* langhooks.c (lhd_tree_size): Likewise.

	* gcc-interface/misc.c (gnat_tree_size): New function.
	(LANG_HOOKS_TREE_SIZE): Redefine.

From-SVN: r253829