amstream: sign-compare fixes.

dlls/amstream/amstream.c

@@ -123,7 +123,7 @@ static HRESULT WINAPI IAMMultiMediaStreamImpl_GetMediaStream(IAMMultiMediaStream
 {
     IAMMultiMediaStreamImpl *This = (IAMMultiMediaStreamImpl *)iface;
     MSPID PurposeId;
-    int i;
+    unsigned int i;
 
     TRACE("(%p/%p)->(%p,%p)\n", This, iface, idPurpose, ppMediaStream);
 

dlls/amstream/main.c

@@ -167,7 +167,7 @@ static const IClassFactoryVtbl DSCF_Vtbl =
  */
 HRESULT WINAPI DllGetClassObject(REFCLSID rclsid, REFIID riid, LPVOID *ppv)
 {
-    int i;
+    unsigned int i;
     IClassFactoryImpl *factory;
     
     TRACE("(%s,%s,%p)\n", debugstr_guid(rclsid), debugstr_guid(riid), ppv);