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/hooks/graphics/backends/d3d9/d3d9_backend.cpp

@@ -278,7 +278,7 @@ static bool is_dx9_on_12_enabled() {
     }
 
     if (GRAPHICS_9_ON_12_STATE == DX9ON12_FORCE_ON) {
-        if (avs::game::is_model("LDJ") && avs::game::is_ext(2023091500, MAXINT)) {
+        if (avs::game::is_model("LDJ") && avs::game::is_ext(2023091500, INT_MAX)) {
             deferredlogs::defer_error_messages({
                 "dx9on12 was force enabled by user (-dx9on12)",
                 "    IIDX31+ is known to be incompatible with DX 9on12, leading to blank screen or crashes",
@@ -1570,4 +1570,4 @@ void update_backbuffer_dimensions(D3DPRESENT_PARAMETERS *params) {
             params->BackBufferHeight);
         return;
     }
-}
+}