Add {get,set}domainname(2)

{get,set}domainname aren't in POSIX but are widely-implemented
extensions.

The Linux kernel provides a setdomainname syscall but not a symmetric
getdomainname syscall, since it expects userspace to get the domain name
from uname(2).

Change-Id: I96726c242f4bb646c130b361688328b0b97269a0
Signed-off-by: Greg Hackmann <ghackmann@google.com>
diff --git a/libc/libc.mips.brillo.map b/libc/libc.mips.brillo.map
index bdd9faa..c5b1bd3 100644
--- a/libc/libc.mips.brillo.map
+++ b/libc/libc.mips.brillo.map
@@ -1257,7 +1257,9 @@
 
 LIBC_O {
   global:
+    getdomainname;
     pthread_getname_np;
+    setdomainname;
 } LIBC_N;
 
 LIBC_PRIVATE {