Clean up irange self tests.

Clean up irange self tests.

Currently we have all the irange and range-op tests in range-op.cc.
This patch splits them up into the appropriate file (irange
tests in value-range.cc and range-op tests in range-op.cc).  The patch
also splits up the tests themselves by functionality.  It's not perfect,
but significantly better than the mess we had.

gcc/ChangeLog:

	* function-tests.c (test_ranges): Call range_op_tests.
	* range-op.cc (build_range3): Move to value-range.cc.
	(range3_tests): Same.
	(int_range_max_tests): Same.
	(multi_precision_range_tests): Same.
	(range_tests): Same.
	(operator_tests): Split up...
	(range_op_tests): Split up...
	(range_op_cast_tests): ...here.
	(range_op_lshift_tests): ...here.
	(range_op_rshift_tests): ...here.
	(range_op_bitwise_and_tests): ...here.
	* selftest.h (range_op_tests): New.
	* value-range.cc (build_range3): New.
	(range_tests_irange3): New.
	(range_tests_int_range_max): New.
	(range_tests_legacy): New.
	(range_tests_misc): New.
	(range_tests): New.