irange_allocator class

irange_allocator class

This is the irange storage class.  It is used to allocate the
minimum amount of storage needed for a given irange.  Storage is
automatically freed at destruction of the storage class.

It is meant for long term storage, as opposed to int_range_max
which is meant for intermediate temporary results on the stack.

The general gist is:

	irange_allocator alloc;

	// Allocate an irange of 5 sub-ranges.
	irange *p = alloc.allocate (5);

	// Allocate an irange of 3 sub-ranges.
	irange *q = alloc.allocate (3);

	// Allocate an irange with as many sub-ranges as are currently
	// used in "some_other_range".
	irange *r = alloc.allocate (some_other_range);

gcc/ChangeLog:

	* value-range.h (class irange): Add irange_allocator friend.
	(class irange_allocator): New.