Test failure on Fedora i686

Interestingly the arm 32 bit build passes and all 64 bit platforms pass, but on i686 I get the following:

```
24/36 Test #20: Imath.testFun ...........................Subprocess aborted***Exception: 0.09 sec
Testing functions in ImathFun.h
floor
ceil
trunc
divs / mods
divp / modp
successor, predecessor
f 0
sf 1.40129846e-45
pf -1.40129846e-45
spf -0
psf 0
f -0
sf 1.40129846e-45
pf -1.40129846e-45
spf -0
psf 0
f 1
sf 1.00000012
pf 0.99999994
spf 1
psf 1
f -1
sf -0.99999994
pf -1.00000012
spf -1
psf -1
f 16
sf 16.0000019
pf 15.999999
spf 16
psf 16
f 7
sf 7.00000048
pf 6.99999952
spf 7
psf 7
f 0.699999988
sf 0.700000048
pf 0.699999928
spf 0.699999988
psf 0.699999988
f inf
sf inf
pf inf
spf inf
psf inf
f -inf
sf -inf
pf -inf
spf -inf
psf -inf
f nan
sf nan
pf nan
spf nan
psf nan
ImathTest: /builddir/build/BUILD/Imath-3.0.2/src/ImathTest/testFun.cpp:70: void testf(float, bool): Assertion `bit_cast (pf) == bit_cast (f)' failed.
```

Full log here:
https://kojipkgs.fedoraproject.org//work/tasks/9350/68939350/build.log

Reproduce the failure on Fedora i686 using the Imath test suite, then start with src/ImathTest/testFun.cpp around testf() and its assertion, followed by ImathFun.h. Compare the float predecessor behavior shown in the log with the passing 32-bit ARM and 64-bit results; done means Imath.testFun passes on i686 without regressing those platforms.

Written by the indexing model from the issue text.