Moved ImGuiColumnsFlags erroneously forward declared in imgui.h + demo bit.

imgui.h

@@ -138,7 +138,6 @@ typedef int ImDrawListFlags;        // -> enum ImDrawListFlags_      // Flags: f
 typedef int ImFontAtlasFlags;       // -> enum ImFontAtlasFlags_     // Flags: for ImFontAtlas
 typedef int ImGuiBackendFlags;      // -> enum ImGuiBackendFlags_    // Flags: for io.BackendFlags
 typedef int ImGuiColorEditFlags;    // -> enum ImGuiColorEditFlags_  // Flags: for ColorEdit4(), ColorPicker4() etc.
-typedef int ImGuiColumnsFlags;      // -> enum ImGuiColumnsFlags_    // Flags: for Columns(), BeginColumns()
 typedef int ImGuiConfigFlags;       // -> enum ImGuiConfigFlags_     // Flags: for io.ConfigFlags
 typedef int ImGuiComboFlags;        // -> enum ImGuiComboFlags_      // Flags: for BeginCombo()
 typedef int ImGuiDragDropFlags;     // -> enum ImGuiDragDropFlags_   // Flags: for BeginDragDropSource(), AcceptDragDropPayload()

imgui_demo.cpp

@@ -2606,6 +2606,7 @@ static void ShowDemoWindowColumns()
                 ImGui::Separator();
             ImGui::Text("%c%c%c", 'a' + i, 'a' + i, 'a' + i);
             ImGui::Text("Width %.2f", ImGui::GetColumnWidth());
+            ImGui::Text("Avail %.2f", ImGui::GetContentRegionAvail().x);
             ImGui::Text("Offset %.2f", ImGui::GetColumnOffset());
             ImGui::Text("Long text that is likely to clip");
             ImGui::Button("Button", ImVec2(-FLT_MIN, 0.0f));

imgui_internal.h

@@ -91,6 +91,7 @@ struct ImGuiWindowSettings;         // Storage for window settings stored in .in
 // Use your programming IDE "Go to definition" facility on the names of the center columns to find the actual flags/enum lists.
 typedef int ImGuiLayoutType;            // -> enum ImGuiLayoutType_         // Enum: Horizontal or vertical
 typedef int ImGuiButtonFlags;           // -> enum ImGuiButtonFlags_        // Flags: for ButtonEx(), ButtonBehavior()
+typedef int ImGuiColumnsFlags;          // -> enum ImGuiColumnsFlags_       // Flags: BeginColumns()
 typedef int ImGuiDragFlags;             // -> enum ImGuiDragFlags_          // Flags: for DragBehavior()
 typedef int ImGuiItemFlags;             // -> enum ImGuiItemFlags_          // Flags: for PushItemFlag()
 typedef int ImGuiItemStatusFlags;       // -> enum ImGuiItemStatusFlags_    // Flags: for DC.LastItemStatusFlags