utmpx api for linux musl.

close rust-lang#3190

(backport <rust-lang#3213>)
(cherry picked from commit e3caaf6)

Author: devnexen

libc-test/semver/linux-musl.txt

@@ -72,17 +72,26 @@ aio_suspend
 aio_write
 aiocb
 asctime_r
+asctime_r
+basename
 basename
 clock_adjtime
 copy_file_range
 ctermid
 dirname
+dirname
 eaccess
+eaccess
+endutxent
+euidaccess
 euidaccess
 explicit_bzero
 futimes
 getauxval
 getloadavg
+getutxent
+getutxid
+getutxline
 lio_listio
 ntptimeval
 open_wmemstream
@@ -94,8 +103,13 @@ prlimit
 prlimit64
 process_vm_readv
 process_vm_writev
+pututxline
 pwritev2
 pwritev64
 reallocarray
+setutxent
+strftime
+strftime_l
+strptime
 tcp_info
 timex

src/unix/linux_like/linux/musl/mod.rs

@@ -993,6 +993,13 @@ extern "C" {
         actions: *mut ::posix_spawn_file_actions_t,
         fd: ::c_int,
     ) -> ::c_int;
+
+    pub fn getutxent() -> *mut utmpx;
+    pub fn getutxid(ut: *const utmpx) -> *mut utmpx;
+    pub fn getutxline(ut: *const utmpx) -> *mut utmpx;
+    pub fn pututxline(ut: *const utmpx) -> *mut utmpx;
+    pub fn setutxent();
+    pub fn endutxent();
 }
 
 // Alias <foo> to <foo>64 to mimic glibc's LFS64 support