Implement RtlCopySecurityDescriptor.

diff --git a/include/winternl.h b/include/winternl.h
index 319bc78..b5e0505 100644
--- a/include/winternl.h
+++ b/include/winternl.h
@@ -1787,6 +1787,7 @@
 void      WINAPI RtlCopyLuid(PLUID,const LUID*);
 void      WINAPI RtlCopyLuidAndAttributesArray(ULONG,const LUID_AND_ATTRIBUTES*,PLUID_AND_ATTRIBUTES);
 BOOLEAN   WINAPI RtlCopySid(DWORD,PSID,PSID);
+NTSTATUS  WINAPI RtlCopySecurityDescriptor(PSECURITY_DESCRIPTOR,PSECURITY_DESCRIPTOR);
 void      WINAPI RtlCopyString(STRING*,const STRING*);
 void      WINAPI RtlCopyUnicodeString(UNICODE_STRING*,const UNICODE_STRING*);
 NTSTATUS  WINAPI RtlCreateAcl(PACL,DWORD,DWORD);