Some utmp symbols still missing on musl

[Ecordonnier]

This is a follow-up of #3190

The function utmpxname is missing from the musl implementation ( src/unix/linux_like/linux/musl/mod.rs ), even though this function is implemented (as a stub doing nothing) in musl (see https://git.musl-libc.org/cgit/musl/tree/include/utmpx.h ).

As reference, see this commit which added the function for solaris, as well as the man page: https://linux.die.net/man/3/endutxent

The symbols "libc::__UT_HOSTSIZE", "libc::__UT_LINESIZE", "libc::__UT_NAMESIZE" and "libc::ACCOUNTING" are also missing.