fix various minor issues causing compilation failure with clang (#567)

- Include order and forward decls were breaking button.h because a
declared but not defined struct can't be initiated (honestly this file
was cooked, crazy include order).
- `MAXINT` is GCC specific, `INT_MAX` is portable.
- InterlockedDecrement takes a LONG, not ULONG
- an imgui printf-style call using a direct string instead of %s (let's
ignore the fact that it's actually safe based on how the str is
constructed)
- missing `override` on a virtual subclass
- `CALLBACK` on a lambda threw me for a loop, but I believe moving it
after the arg list is the correct approach (see if it builds on gcc I
guess)
- `std::result_of` was removed in C++20, which the project is built with

src/spice2x/overlay/windows/screen_resize.h

@@ -10,8 +10,8 @@ namespace overlay::windows {
         ~ScreenResize() override;
 
         void build_content() override;
-        void update();
-        
+        void update() override;
+
     private:
         size_t toggle_screen_resize = ~0u;
         bool toggle_screen_resize_state = false;