Add sethostname(2).

Not very useful, but helps building stuff like toybox out of the box.

Change-Id: I110e39030452bd093a84278e019c5752d293718d
diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index 866671d..39ff37d 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -313,6 +313,8 @@
 int setfsgid(gid_t)  all
 int setfsuid(uid_t)  all
 
+int sethostname(const char*, size_t)  all
+
 pid_t wait4(pid_t, int*, int, struct rusage*)  all
 int __waitid:waitid(int, pid_t, struct siginfo_t*, int, void*)  all