NAME
    qprepDirectiveAssign: assign directive value to directive key


  USAGE
    qprepDirectiveAssign(\%state_table, \%message_table,
                         $directive_key, $directive_value);


  ARGUMENTS
   \%state_table (in/out): reference to hash table of qprep properties

   \%message_table (in): nested hash table of error messages and codes.
     (See qprepMessageTableInitialize(3))

   $directive_key (in): string containing directive key

   $directive_value (in): string containing directive key


  DESCRIPTION
    This routine assigns the given directive value to the given directive
    key in the qprep state table.  This routine also performs a simple
    check to verify that the table already has an entry for the given
    key, to make sure that the key is valid.  If the state table does
    not already have the key then this routine prints a warning message
    but makes the assignment anyway.

    qprepDirectiveParse calls this routine before any translations.


  RETURN VALUE
    This routine always returns 0.


  SEE ALSO
    qprepStateInitialize(in 'qprep.pm'),
    qprepDirectiveParse(in 'qprep.pm')


  NOTES
    To clarify:  this routine modifies an entry in state_table only.
    This routine does not modify the contents of directive_key nor
    directive_value, nor could it since those arguments are scalars,
    not references to scalars.