Make gcc::context be GC-managed

Make gcc::context be GC-managed

	* Makefile.in (GTFILES): Add context.h.
	* context.c (gcc::context::operator new): New.
	(gcc::context::gt_ggc_mx): New.
	(gcc::context::gt_pch_nx): New.
	(gcc::context::gt_pch_nx): New.
	* context.h (gcc::context): Add GTY((user)) marking.
	(gcc::context::operator new): New.
	(gcc::context::gt_ggc_mx): New.
	(gcc::context::gt_pch_nx): New.
	(gcc::context::gt_pch_nx): New.
	(g): Add GTY marking.
	(gt_ggc_mx (gcc::context *)): New.
	(gt_pch_nx (gcc::context *)): New.
	(gt_pch_nx (gcc::context *ctxt, gt_pointer_operator op,
	void *cookie)): New.
	* gengtype.c (open_base_files) <ifiles>: Add context.h.

From-SVN: r201864