Function:   DtChkDteFmt( <expC> ) --> array

Synopsis:   Accepts a dateformat string and checks its validity.

            <expC1> Date formatstring as used by the SET() function

            Comparison is done according to the country specific
            date formats as defined in CLIPPER when using the
            SET( _SET_DATEFORMAT ) function.

                    country identifiers as defined by CLIPPER:

                            1 = AMERICAN
                            2 = ANSI
                            3 = BRITISH
                            4 = FRENCH
                            5 = GERMAN
                            6 = ITALIAN
                            7 = JAPAN
                            8 = USA

Returns:    an array with 2 elements

            element[1]   contains .T. if dateformat was correct,
                         otherwise .F.
            element[2]   contains the country identifier as defined
                         by CLIPPER if dateformat was correct,
                         otherwise 0