Add selftests for range_contains and insert_into_bit_range_vector

Add selftests for range_contains and insert_into_bit_range_vector

Add some selftests for these two functions.  To to make it easier to
compare sequences of ranges, add operator== and operator!= to compare
two gdb::array_view, and add operator== in struct range.

gdb/ChangeLog:

	* value.c: Include "selftest.h" and "common/array-view.h".
	(struct range) <operator ==>: New.
	(test_ranges_contain): New.
	(check_ranges_vector): New.
	(test_insert_into_bit_range_vector): New.
	(_initialize_values): Register selftests.
	* common/array-view.h (operator==, operator!=): New.