request: increase TTY_NAME_MAX in limits.h

[Laurent Bercot <ska-dietlibc@skarnet.org>]

  Hello,

  TTY_NAME_MAX is currently 20. This is not enough for me. Could it
be increased a bit ?

  Explanation: my /dev is actually a symlink to /mnt/tmpfs/dev, and
ttyname_r() writes fully resolved paths, so "/mnt/tmpfs/dev/pts/0"
is *just* too large to fit into the 20 bytes static buffer provided
by ttyname().
  Impact: it breaks dropbear, which instantly dies when ttyname() fails -
this is a deal breaker for me. Less importantly, it also breaks the %y%
prompt mechanism in zsh, which prints the default "tty" instead of the
correct name.

I'd like to be able to use prebuilt musl toolchains, like Gregor's ones,
or Rob's ones when they come out, so editing limits.h myself won't cut it.
24 bytes would be enough for me to have 10k ptys (which will never happen).
So... can I haz 4 more bytes plz ?

  Thanks,

-- 
  Laurent