Retain older message APIs since existing GPU drivers depend on them.

Change-Id: Ic5425fafb7971b6094108d79346d067785b91735
diff --git a/driver/rsdRuntimeStubs.cpp b/driver/rsdRuntimeStubs.cpp
index f0cd726..8431410 100644
--- a/driver/rsdRuntimeStubs.cpp
+++ b/driver/rsdRuntimeStubs.cpp
@@ -546,7 +546,7 @@
 
 static uint32_t SC_ToClient(int cmdID) {
     Context *rsc = RsdCpuReference::getTlsContext();
-    return rsrToClient(rsc, cmdID, NULL, 0);
+    return rsrToClient(rsc, cmdID, (const void *)NULL, 0);
 }
 
 static uint32_t SC_ToClientBlocking2(int cmdID, const void *data, uint32_t len) {
@@ -556,7 +556,7 @@
 
 static uint32_t SC_ToClientBlocking(int cmdID) {
     Context *rsc = RsdCpuReference::getTlsContext();
-    return rsrToClientBlocking(rsc, cmdID, NULL, 0);
+    return rsrToClientBlocking(rsc, cmdID, (const void *)NULL, 0);
 }