Tables: Ditch old columns flags/setting if not called again. Displaying right-most border when using _SameWidths. Moving Width-related functions to their own section.

Effectively removed the TableFixColumnFlags() in first loop of TableUpdateLayout() to replace it with similar one but only when column not declared. I think this should be the right thing.

Author: ocornut

imgui_internal.h

@@ -2301,6 +2301,7 @@ namespace ImGui
     IMGUI_API void          TableSetupDrawChannels(ImGuiTable* table);
     IMGUI_API void          TableUpdateLayout(ImGuiTable* table);
     IMGUI_API void          TableUpdateBorders(ImGuiTable* table);
+    IMGUI_API void          TableUpdateColumnsWeightFromWidth(ImGuiTable* table);
     IMGUI_API void          TableDrawBorders(ImGuiTable* table);
     IMGUI_API void          TableDrawContextMenu(ImGuiTable* table);
     IMGUI_API void          TableMergeDrawChannels(ImGuiTable* table);