version into different directories. Which version a given port uses is
controlled by the SOFTFLOAT_BITS make variable. This is set to 64 (which
uses the same code we had before) by default. 32-bit platforms that don't
need extended precision support might get better performance by using 32.
Set the ARM port to use the 32-bit version of SoftFloat, since this is more
than a factor of two faster than the 64-bit version. This should get the
floating-point performance back to what it was in 1.5.
