Remove GTY support for vrange and derived classes.

Remove GTY support for vrange and derived classes.

Now that we have a vrange storage class to save ranges in long-term
memory, there is no need for GTY markers for any of the vrange
classes, since they should never live in GC.

gcc/ChangeLog:

	* value-range-storage.h: Remove friends.
	* value-range.cc (gt_ggc_mx): Remove.
	(gt_pch_nx): Remove.
	* value-range.h (class vrange): Remove GTY markers.
	(class irange): Same.
	(class int_range): Same.
	(class frange): Same.
	(gt_ggc_mx): Remove.
	(gt_pch_nx): Remove.