Real: fix integer overflow

This is trivially exploitable to run code.

Pointed-out-by: Tobias Klein
(cherry picked from commit eb9963eb)

modules/demux/real.c

@@ -932,16 +932,13 @@ static void ReadRealIndex( demux_t *p_demux )
         msg_Dbg( p_demux, "Real Index: Does next index exist? %d ",
                         GetDWBE( &buffer[16] )  );
 
-    p_sys->p_index = 
-            (rm_index_t *)malloc( sizeof( rm_index_t ) * (i_index_count+1) );
+    p_sys->p_index = calloc( i_index_count + 1, sizeof( rm_index_t ) );
     if( p_sys->p_index == NULL )
     {
         msg_Err( p_demux, "Memory allocation error" ); 
         return;
     }
 
-    memset( p_sys->p_index, 0, sizeof(rm_index_t) * (i_index_count+1) );
-
     for( i=0; i<i_index_count; i++ )
     {
         if( stream_Read( p_demux->s, buffer, 14 ) < 14 )