fix shell command injection
add way to test command under windows
change command to which available under most unix systems

agree i will change it which is available under suse, ubuntu, debian, fedora, bsd
Merge branch '2.3' into 2.4

* 2.3:
  [HttpKernel] added an analyze of environment parameters for built-in server.
  change command to which available under most unix systems
  add way to test command under windows
  fix shell command injection
  [Form] allowed CallbackTransformer to use callable
  [Process] Added process synchronization to the incremental output tests