Get Tru64/cc to compile. Need to add -ieee so that it doesn't choke on

Get Tru64/cc to compile.  Need to add -ieee so that it doesn't choke on
0.0/0.0.  That option appears to affect the regression test result as well.
The compiler documentation doesn't recommend -O4 for universal use, so
let's stick to the conservative -O (== -O2) by default.