FIX: issue #877 (Output float! value incorrectly on Linux-ARM.)

A zero 32-bit value is now set to "hole" registers when passing 64-bit values following AAPCS (though, this is not documented in the official docs). Ex:

    printf ["%.14g" 1.23]
       -> r0: "%.14g"
       -> r1: 0
       -> r2/r3: 1.23