Backends: SDL2, SDL3: maximum room for sanitizer to not be zealous.

backends/imgui_impl_sdl2.cpp

@@ -136,7 +136,7 @@ struct ImGui_ImplSDL2_Data
     SDL_Renderer*           Renderer;
     Uint64                  Time;
     char*                   ClipboardTextData;
-    char                    BackendPlatformName[40];
+    char                    BackendPlatformName[48];
 
     // Mouse handling
     Uint32                  MouseWindowID;

backends/imgui_impl_sdl3.cpp

@@ -102,7 +102,7 @@ struct ImGui_ImplSDL3_Data
     SDL_Renderer*           Renderer;
     Uint64                  Time;
     char*                   ClipboardTextData;
-    char                    BackendPlatformName[40];
+    char                    BackendPlatformName[48];
 
     // IME handling
     SDL_Window*             ImeWindow;