Examples: Allegro 5: Properly destroy all globals on shutdown. (#2262)

docs/CHANGELOG.txt

@@ -74,6 +74,7 @@ Other Changes:
 - Demo: Added a few more things under "Child windows" (changing ImGuiCol_ChildBg, positioning child, using IsItemHovered after a child).
 - Examples: DirectX10/11/12: Made imgui_impl_dx10/dx11/dx12.cpp link d3dcompiler.lib from the .cpp file
   to ease integration.
+- Examples: Allegro 5: Properly destroy globals on shutdown to allow for restart. (#2262) [@DomRe]
 
 
 -----------------------------------------------------------------------

examples/imgui_impl_allegro5.cpp

@@ -280,9 +280,14 @@ bool ImGui_ImplAllegro5_Init(ALLEGRO_DISPLAY* display)
 void ImGui_ImplAllegro5_Shutdown()
 {
     ImGui_ImplAllegro5_InvalidateDeviceObjects();
+
     g_Display = NULL;
+    g_Time = 0.0;
+
+    if (g_VertexDecl)
+        al_destroy_vertex_decl(g_VertexDecl);
+    g_VertexDecl = NULL;
 
-    // Destroy last known clipboard data
     if (g_ClipboardTextData)
         al_free(g_ClipboardTextData);
     g_ClipboardTextData = NULL;