Written Jan 1988 by Paul Heitner, Bramalea, Ontario.
	Placed in the Public Domain.  The author disclaims any
	responsibility for possible adverse consequences resulting
	from the use of this code.

  GetEnvStr - This function takes a SET parameter and returns the
  string value associated with that parameter.

  Input requirements are:
        Valid SET parameter in UpperCase (like 'COMSPEC')

  Outputs are:
        The value of the supplied SET parameter in a String type if the
        parameter exists in the environment, else a null string if the
		parameter cannot be found.  If given a null string parameter
		GetEnvStr will return a null string.

  credits:
    -  Bela Lubkin
    -  Stuart Fuller
	-  Paul Heitner (Turbo Pascal 4.0 version)