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/games/iidx/local_camera.h

@@ -89,7 +89,7 @@ namespace games::iidx {
     protected:
         virtual ~IIDXLocalCamera() {};
 
-        ULONG m_nRefCount;
+        LONG m_nRefCount;
         CRITICAL_SECTION m_critsec;
 
         std::string m_name;