Add float*_unordered() functions to softfloat, matching the softfloat-native
ones. Also add float*_unordered_quiet() functions to match the others
comparison functions.

This allow target-i386/ops_sse.h to be compiled with softfloat.
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>