rpcrt4: Cast-qual warnings fix (2 of 2)

[Andrew Talbot]

Changelog:
    rpcrt4: Cast-qual warning fix.

diff -urN a/dlls/rpcrt4/ndr_stubless.c b/dlls/rpcrt4/ndr_stubless.c
--- a/dlls/rpcrt4/ndr_stubless.c	2006-11-10 17:26:30.000000000 +0000
+++ b/dlls/rpcrt4/ndr_stubless.c	2006-11-11 14:37:07.000000000 +0000
@@ -812,7 +812,7 @@
     if (pProcHeader->Oi_flags & RPC_FC_PROC_OIF_OBJECT)
     {
         /* object is always the first argument */
-        This = **(void ***)(&pFormat+1);
+        This = **(void *const **)(&pFormat+1);
         NdrProxyInitialize(This, &rpcMsg, &stubMsg, pStubDesc, procedure_number);
     }
     else