message: Internals: Remove requirement to define IMGUI_DEFINE_PLACEMENT_NEW
diff: // (internals)
  // You may use this file to debug, understand or extend ImGui features but we don't provide any guarantee of forward compatibility!
  -// Implement maths operators for ImVec2 (disabled by default to not collide with using IM_VEC2_CLASS_EXTRA along with your own math types+operators)
  +// Set:
  // #define IMGUI_DEFINE_MATH_OPERATORS
  -// Define IM_PLACEMENT_NEW() macro helper.
  -// #define IMGUI_DEFINE_PLACEMENT_NEW
  +// To implement maths operators for ImVec2 (disabled by default to not collide with using IM_VEC2_CLASS_EXTRA along with your own math types+operators)
  #pragma once
  @@ -159,12 +158,10 @@ static inline float ImLinearSweep(float current, float target, float speed)
  // We call C++ constructor on own allocated memory via the placement "new(ptr) Type()" syntax.
  // Defining a custom placement new() with a dummy parameter allows us to bypass including <new> which on some platforms complains when user has disabled exceptions.
  -#ifdef IMGUI_DEFINE_PLACEMENT_NEW
  struct ImPlacementNewDummy {};
  inline void* operator new(size_t, ImPlacementNewDummy, void* ptr) { return ptr; }
  inline void operator delete(void*, ImPlacementNewDummy, void*) {}
  #define IM_PLACEMENT_NEW(_PTR) new(ImPlacementNewDummy(), _PTR)
  -#endif
  //-----------------------------------------------------------------------------
  // Types
  