[frange] Remove special casing from unordered operators.

[frange] Remove special casing from unordered operators.

In coming up with testcases for the unordered folders, I realized that
we were already handling them correctly, even in the absence of my
work in this area lately.

All of the unordered fold_range() methods try to fold with the ordered
variants first, and if they return TRUE, we are guaranteed to be able
to fold, even in the presence of NANs.  For example:

if (x_5 >= y_8)
  if (x_5 __UNLE y_8)

On the true side of the first conditional we know that either x_5 < y_8
or that one or more operands is a NAN.  Since UNLE_EXPR returns true
for precisely this scenario, we can fold as true.

This is handled in the fold_range() methods as follows:

    if (!range_op_handler (LE_EXPR).fold_range (r, type, op1_no_nan,
						op2_no_nan, trio))
      return false;
    // The result is the same as the ordered version when the
    // comparison is true or when the operands cannot be NANs.
    if (!maybe_isnan (op1, op2) || r == range_true (type))
      return true;

This code has been there since the last release, and makes the special
casing I am deleting obsolete.  I have added tests to make sure we
keep track of this behavior.

gcc/ChangeLog:

	* range-op-float.cc (foperator_unordered_ge::fold_range): Remove
	special casing.
	(foperator_unordered_gt::fold_range): Same.
	(foperator_unordered_lt::fold_range): Same.
	(foperator_unordered_le::fold_range): Same.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/vrp-float-relations-5.c: New test.
	* gcc.dg/tree-ssa/vrp-float-relations-6.c: New test.