Replace large timeout (1024*1024*1024) using real-time clock timeout (10 seconds default)

Change SHARED_MEMORY_MAGIC_NUMBER to make sure server/client are using the same version (shared memory)
add --realtimesimulation to physics server (GUI, VR)
remove --G Xcode from build_cmake_pybullet_double.sh

examples/SharedMemory/SharedMemoryBlock.h

@@ -1,9 +1,9 @@
 #ifndef SHARED_MEMORY_BLOCK_H
 #define SHARED_MEMORY_BLOCK_H
 
-#define SHARED_MEMORY_MAGIC_NUMBER 64738
 #define SHARED_MEMORY_MAX_COMMANDS 4
 
+
 #include "SharedMemoryCommands.h"
 
 struct SharedMemoryBlock