module `DivSqrtRecF64_mulAddZ31'.

greater-than), and associated tests.

thorough testing.

No need to handle exponent and significant separately.

We failed to kill the excess precision.

Support for autometad regression testing

This runs the tests for a fixed amount of time, as opposed to just
running them until they find 20 failures.  This makes the test harness
suitable for running automatically.

In order to run the standalone tests we need to be able to run
"testfloat_gen", part of the TestFloat-3 package.  Since this is
probably going to be something that's not commonly installed, I added
some Makefile targets that download and build "testfloat_gen" so it
can be run without messing around with any system dependencies.

Note that TestFloat-3 by default builds in 8086 mode, so there's a
patch here that makes it build in RISC-V mode instead.

so that NaN results always have negative sign.

getting ready to integrate the div/sqrt unit.