Add <sys/quota.h>.

It turns out that at least the Nexus 9 kernel is built without CONFIG_QUOTA.
If we decide we're going to mandate quota functionality, I'm happy for us to
be a part of CTS that ensures that happens, but I don't want to be first, so
there's not much to test here other than "will it compile?". The strace
output looks right though.

Bug: http://b/27948821
Bug: http://b/27952303
Change-Id: If667195eee849ed17c8fa9110f6b02907fc8fc04
diff --git a/libc/libc.arm.map b/libc/libc.arm.map
index 40f645c..fa83528 100644
--- a/libc/libc.arm.map
+++ b/libc/libc.arm.map
@@ -1277,6 +1277,7 @@
     getsubopt;
     hasmntopt;
     pthread_getname_np;
+    quotactl;
     setdomainname;
     sighold;
     sigignore;