BUG 254
=======
Original Bug:

This is what the current expression library has for an error check on the atanh
function:

double
300             PTatanh(arg)
301                 double arg;
302             {
303                 if (fabs(arg) > 20)
304                   return 1.;

which is totally wrong.  It looks like a check for tanh (which plateaus at
+-20) but this would be wrong for that as well since it ignores the negative
side of the number line.

It is probably worthwhile to actually put the *correct* bounds (+- 20) on the
tanh since it probably calls cosh and sinh underneath which will blow up for
large arguments.

Bug Repaired in Xyce Version 1.1

This test checks that the bsource functions "tanh" and "atanh" work correctly,
varying from 1 to -1 as the argument varies.  In particular, the test pushes
the argument from 100 to -100 even though the functions plateau out at
approximately +-20 and +-1, respectively, depending on numerics.  This test
should run to completion and produce data which "matches" that in the given
.prn file.  I (SAH) checked using the xyce_verify test but it should work fine
using either the "box" compare or the xyce_verify.

Parallel testing is not needed for this case.
