property_service: log pid,uid and gid of setprop client

When auditing setprop denials, it is often unclear of who the process is
in a multi-process domain. To help identify the invoker, log the pid, uid,
and gid of the caller.

Before:
avc:  denied  { set } for property=wifi.xxx ...

After:
avc:  denied  { set } for property=wifi.xxx pid=30691 uid=123 gid=345 ...

Change-Id: I5cdcb3d18fbd52e0987b5e1497b9f6620c6c742a
Signed-off-by: William Roberts <william.c.roberts@intel.com>
diff --git a/init/property_service.h b/init/property_service.h
index 51d7404..1a48fb1 100644
--- a/init/property_service.h
+++ b/init/property_service.h
@@ -18,9 +18,15 @@
 #define _INIT_PROPERTY_H
 
 #include <stddef.h>
+#include <sys/socket.h>
 #include <sys/system_properties.h>
 #include <string>
 
+struct property_audit_data {
+    ucred *cr;
+    const char* name;
+};
+
 extern void property_init(void);
 extern void property_load_boot_defaults(void);
 extern void load_persist_props(void);