Clean up more of our floating-point cruft.

Clean up more of our floating-point cruft.

There was a ton of unused stuff here. I was hoping to kill all our
C-style casts so I could turn -Wold-style-cast on, but it looks like
our header files are too full of C-style casts for that to be practical
in conjunction with -Werror.

I'll get rid of the remaining C-style casts in the more heavily maintained
files at some point, but I'm calling it a day on the floating-point stuff
for now.

Change-Id: I93ce1c4a9db27674f4db1f329d6e7fa27e81ad72