[PR tree-optimization/107355] Handle NANs in abs range-op entry.

[PR tree-optimization/107355] Handle NANs in abs range-op entry.

The problem here is that the threader is coming up with a path where
the only valid result is a NAN.  When the abs op1_range entry is
trying to add the negative posibility, it attempts to get the bounds
of the working range.  NANs don't have bounds so they need to be
special cased.

	PR tree-optimization/107355

gcc/ChangeLog:

	* range-op-float.cc (foperator_abs::op1_range): Handle NAN.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/pr107355.c: New test.