Environment Editing Routines:
  Overview        About these routines
  XPsetEnv()      Replace or Insert a new environment variable
  XPdelEnv()      Delete an environment variable
  XPreadEnv()     Read an environment string from the original Env.
  XPenvUsed()     Return the number of bytes currently in use by ENV.
  XPenvSize()     Return the number of bytes reserved for the Environment
  XPenvOrig()     Return Pointer to original Environment strings.
  XPenvPtr()      Return/Set the Environment Pointer
  XPenvCount()    The Count of Enviroment strings
  XPenvStr()      Return the Nth string of the environment
  XPenvDel()      Delete the Nth string of the environment
  XPenvAdd()      Add a string to the environment strings.