Get gcc to do strict IEEE math. This flag was already used for cc, just not

Get gcc to do strict IEEE math.  This flag was already used for cc, just not
gcc.  Without this flag, doing pretty much anything with NaNs causes
a Floating Point Exception signal.  This causes the interpreter to quit.
The failing tests this fixes are:  test_float, test_long, and test_struct.
This is somewhat equivalent to doing signal(SIGFPE, SIG_IGN).

Will verify if this is a problem in 2.4 and backport if necessary (probably).