= Tab display

        TAB {on [altch] | off | clear | =default | nn [asdefault] }
            on      :display tab char and DBCS(Japanese) space.
                     Char used to display tab and its following space
                     is customizable by .INI file parameter.
                     Default is Tab       :Up-arrow
                                Tab-skip  :Right arrow
                                DBCS space:shadow box
            off     :tab char is not displayed.
                     Special char for un-displayable char
                     is always displayed regardless this option.
            clear   :remove tab with space remained.
            =default:set this file's tabctr to the default setting.
            nn      :Tab column interval,default is 4.
                     With "asdefault", set default tabctr.
                     Without "asdefault", set the tabctr of current opened
                     and profile record is updated.
                     Tab key cause cursor jump not to next tab column
                     but jump to next field when default tab column is 0.
                     Maximum 12.
                     1 is forced to the file opened by record mode.
            altch   :Change char to display TAB/DBCS-space char.
                     On Windows command prompt, unicode character display-column-width depends its font settiong.
                     If you use ASCII char as alt-displaying-char of TAB and TAB padding space char.
                     If you yet use preferred unicode for TAB and TAB padding, use this altch option.
                     On wxe,gxe,Linux xe, it may not be occur.
                     Default is U-21be(display TAB:0x09), U-21c0(Display spaces skipped by TAB)
                     and U-2591(DBCS-space),
                     This option overrides following INI file options.
                       (J)Tab_disp_char  =FFFF #(FFFF)# Tab display char for Japanese mode. (FFFF means U-21be & U-21c0)
                       (E)Tab_disp_char  =FFFF #(FFFF)# Tab display char for English  mode. (FFFF means U-21be & U-21c0)
                       DBCSspace_dispchar=FF #(FF)# DBCS space display char. (FF means U-2591)
                     "tab on 000" is used to back to default(u21be-21c0,2591) or INI settings.
                     ex)  tab on "^-" ,   tab on u25b8-25b9 ,  tab on "^-!" ,  tab on u25b8-25b9-21be.
                     When Non-ASCII is specified as altch, "xpr -tabon" cmd use the altch
                     for printing CPU8 file and use 0x18 and 0x1a for non-CPU8 file.