analyzer: split out struct bit_range from class concrete_binding

analyzer: split out struct bit_range from class concrete_binding

gcc/analyzer/ChangeLog:
	* store.cc (concrete_binding::dump_to_pp): Move bulk of
	implementation to...
	(bit_range::dump_to_pp): ...this new function.
	(bit_range::cmp): New.
	(concrete_binding::overlaps_p): Update for use of bit_range.
	(concrete_binding::cmp_ptr_ptr): Likewise.
	* store.h (struct bit_range): New.
	(class concrete_binding): Replace fields m_start_bit_offset and
	m_size_in_bits with new field m_bit_range.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>