Comparing NaN with bignums yields FPE

Imported from http://bugzilla.roxen.com/bugzilla/show_bug.cgi?id=4605

Reported by Martin Karlgren marty@roxen.com

Pike v7.4 release 528 running Hilfe v3.5 (Incremental Pike Frontend)
> float kNAN = sscanf("\x7f\xf8\0\0\0\0\0\0", "%8F", float _NAN) && _NAN;
> pow(2, 32) > kNAN;
Floating point exception

$ uname -a Darwin gabrielle.roxen.com 9.3.0 Darwin Kernel Version 9.3.0: Fri May 23 00:49:16 PDT 2008; root:xnu-1228.5.18~1/RELEASE_I386 i386