Zero byte-compiler warnings in the test suite

[Stefan Kangas]

Dear emacs-devel,

I would like to bring to your attention that we now have a test suite
with no byte-compiler warnings.  This is nice, as there is less noise,
and it will be easier to spot real problems.

In my use, I'm happy that I can now look at a soothing zero in the mode
line of my *Compilation* buffer when saying "make && make check".  ;-)

Thanks to everyone who helped with this.