Function:    ReadEnv()

               Just like Clipper's GetEnv(), but changes made with SetEnv()
               are correctly refelected here.

  Syntax:      ReadEnv(cVar)

  Arguments:   <cVar> is the variable one wishes to read.

  Returns:     The Environment's variable value, or "" when
               it is not found.

  Usage:       * Assuming PROMPT is $p$g
               SetEnv('PROMPT','(Shell) '+GetEnv('PROMPT'))
               ? ReadEnv('PROMPT')  && Returns "(Shell) $p$g"
               ? GetEnv('PROMPT')   && Returns "$p$g"