Value Range: Add range op for builtin isfinite

Value Range: Add range op for builtin isfinite

The former patch adds optab for builtin isfinite. Thus builtin isfinite
might not be folded at front end.  So the range op for isfinite is needed
for value range analysis.  This patch adds range op for builtin isfinite.

gcc/
	* gimple-range-op.cc (class cfn_isfinite): New.
	(op_cfn_finite): New variables.
	(gimple_range_op_handler::maybe_builtin_call): Handle
	CFN_BUILT_IN_ISFINITE.

gcc/testsuite/
	* gcc.dg/tree-ssa/range-isfinite.c: New test.