Fix the VCVT instruction. It must round towards zero when converting from
a floating-point to an integer value. This was not the case causing issues
when printing certain values.

There is a VCVTR instruction that will round depending on the current
rounding mode. We don't yet support this instruction, or setting the
rounding mode.
Set the default ABI to the softfp version on armv6. This is compatible with
the existing ABI as it passes floating-point values in ARM regsters. It is
allowed to use VFP instructions as required instead of calling into the
softfloat code.
Build ubldr with soft-float
Update the floating-point control functions for ARM hard-float.
Only support softfp on ARM EABI.