Update langs.model.xml - TCL keyword "then"

Added TCL's optional keyword "then": https://www.tcl.tk/man/tcl8.5/TclCmd/if.htm

Close #15309

PowerEditor/src/langs.model.xml

@@ -406,7 +406,7 @@
             <Keywords name="type2">associativity convenience dynamic didSet final get infix inout lazy left mutating none nonmutating optional override postfix precedence prefix Protocol required right set Type unowned weak willSet</Keywords>
         </Language>
         <Language name="tcl" ext="tcl" commentLine="#">
-            <Keywords name="instre1">after append apply array auto_execok auto_import auto_load auto_load_index auto_qualify auto_reset bgerror binary break catch cd chan clock close concat continue coroutine dde dict default else elseif encoding env eof error eval exec exit expr fblocked fconfigure fcopy file fileevent filename flush for foreach format gets glob global history http if incr info interp join lappend lassign lindex linsert list llength lmap load lrange lrepeat lreplace lreverse lsearch lset lsort memory my namespace next nextto oo::class oo::copy oo::define oo::objdefine oo::object open package parray pid pkg_mkIndex platform proc puts pwd read regexp registry regsub rename return scan seek self set socket source split string subst switch tailcall tclLog tclMacPkgSearch tclPkgSetup tclPkgUnknown tell throw time trace try unknown unload unset update uplevel upvar variable vwait while yield yeildto zlib</Keywords>
+            <Keywords name="instre1">after append apply array auto_execok auto_import auto_load auto_load_index auto_qualify auto_reset bgerror binary break catch cd chan clock close concat continue coroutine dde dict default else elseif encoding env eof error eval exec exit expr fblocked fconfigure fcopy file fileevent filename flush for foreach format gets glob global history http if incr info interp join lappend lassign lindex linsert list llength lmap load lrange lrepeat lreplace lreverse lsearch lset lsort memory my namespace next nextto oo::class oo::copy oo::define oo::objdefine oo::object open package parray pid pkg_mkIndex platform proc puts pwd read regexp registry regsub rename return scan seek self set socket source split string subst switch tailcall tclLog tclMacPkgSearch tclPkgSetup tclPkgUnknown tell then throw time trace try unknown unload unset update uplevel upvar variable vwait while yield yeildto zlib</Keywords>
             <Keywords name="instre2">bell bind bindtags button canvas checkbutton console destroy entry event focus font frame grab grid image label labelframe listbox lower menu menubutton message option pack panedwindow place radiobutton raise scale scrollbar selection send spinbox text tk tkerror tkwait toplevel ttk::button ttk::checkbutton ttk::combobox ttk::entry ttk::frame ttk::intro ttk::label ttk::labeframe ttk::menubutton ttk::notebook ttk::panedwindow ttk::progressbar ttk::radiobutton ttk::scale ttk::scrollbar ttk::sizegrip ttk::spinbox ttk::style winfo wm</Keywords>
             <Keywords name="type1">@scope body class code common component configbody constructor define destructor hull import inherit itcl itk itk_component itk_initialize itk_interior itk_option iwidgets keep method private protected public</Keywords>
             <Keywords name="type2">tkButtonDown tkButtonEnter tkButtonInvoke tkButtonLeave tkButtonUp tkCancelRepeat tkCheckRadioInvoke tkDarken tkEntryAutoScan tkEntryBackspace tkEntryButton1 tkEntryClosestGap tkEntryInsert tkEntryKeySelect tkEntryMouseSelect tkEntryNextWord tkEntryPaste tkEntryPreviousWord tkEntrySeeInsert tkEntrySetCursor tkEntryTranspose tkEventMotifBindings tkFDGetFileTypes tkFirstMenu tkFocusGroup_Destroy tkFocusGroup_In tkFocusGroup_Out tkFocusOK tkListboxAutoScan tkListboxBeginExtend tkListboxBeginSelect tkListboxBeginToggle tkListboxCancel tkListboxDataExtend tkListboxExtendUpDown tkListboxMotion tkListboxSelectAll tkListboxUpDown tkMbButtonUp tkMbEnter tkMbLeave tkMbMotion tkMbPost tkMenuButtonDown tkMenuDownArrow tkMenuDup tkMenuEscape tkMenuFind tkMenuFindName tkMenuFirstEntry tkMenuInvoke tkMenuLeave tkMenuLeftArrow tkMenuMotion tkMenuNextEntry tkMenuNextMenu tkMenuRightArrow tkMenuUnpost tkMenuUpArrow tkMessageBox tkPostOverPoint tkRecolorTree tkRestoreOldGrab tkSaveGrabInfo tkScaleActivate tkScaleButton2Down tkScaleButtonDown tkScaleControlPress tkScaleDrag tkScaleEndDrag tkScaleIncrement tkScreenChanged tkScrollButton2Down tkScrollButtonDown tkScrollButtonUp tkScrollByPages tkScrollByUnits tkScrollDrag tkScrollEndDrag tkScrollSelect tkScrollStartDrag tkScrollToPos  tkScrollTopBottom tkTabToWindow tkTearOffMenu tkTextAutoScan tkTextButton1 tkTextClosestGap tkTextInsert tkTextKeyExtend tkTextKeySelect tkTextNextPara tkTextNextPos tkTextNextWord tkTextPaste tkTextPrevPara tkTextPrevPos tkTextResetAnchor tkTextScrollPages tkTextSelectTo tkTextSetCursor tkTextTranspose tkTextUpDownLine tkTraverseToMenu tkTraverseWithinMenu tk_bisque tk_chooseColor tk_dialog tk_focusFollowsMouse tk_focusNext tk_focusPrev tk_getOpenFile tk_getSaveFile tk_messageBox tk_optionMenu tk_popup tk_setPalette tk_textCopy tk_textCut tk_textPaste</Keywords>