[Toybox] ulimit/prlimit

[Rob Landley]

I added -P to ulimit 2 years ago because there's a prlimit() syscall now and you
can change limits for other pids, and later util-linux added one, but they used
-p instead of -P:

http://man7.org/linux/man-pages/man1/prlimit.1.html

Except -p is pipe buffer size, from ubuntu 14.04's bash:

$ help ulimit | grep pipe
      -p	the pipe buffer size

So the util-linux guys decided to be gratuitously incompatible with existing bash...

I'm pondering making prlimit an alias for ulimit, so still capital -P, and maybe
add --pid as a longopt. but I'm also tempted to just wash my hands of it and go
"ulimit has -P, prlimit is broken".

Anybody have a strong opinion here?

Rob