ranger: Improve a % b operand ranges [PR91029]

As mentioned in the PR, the previous PR91029 patch was testing
op2 >= 0 which is unnecessary, even negative op2 values will work the same,
furthermore, from if a % b > 0 we can deduce a > 0 rather than just a >= 0
(0 % b would be 0), and it actually valid even for other constants than 0,
a % b > 5 means a > 5 (a % b has the same sign as a and a in [0, 5] would
result in a % b in [0, 5].  Also, we can deduce a range for the other
operand, if we know
a % b >= 20, then b must be (in absolute value for signed modulo) > 20,
for a % [0, 20] the result would be [0, 19].

2020-11-19  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/91029
	* range-op.cc (operator_trunc_mod::op1_range): Don't require signed
	types, nor require that op2 >= 0.  Implement (a % b) >= x && x > 0
	implies a >= x and (a % b) <= x && x < 0 implies a <= x.
	(operator_trunc_mod::op2_range): New method.

	* gcc.dg/tree-ssa/pr91029-1.c: New test.
	* gcc.dg/tree-ssa/pr91029-2.c: New test.