Changed SDL_mixer version guard.

SDL_MIXER_COMPILEDVERSION is not in Windows release of mixer v2.0.1, so it is back to basics with SDL_MIXER_PATCHLEVEL.
MIX_INIT_FLUIDSYNTH was renamed in 2.0.2, according to headers from Windows releases.
Ref PR #42, #46

SpaceCadetPinball/Sound.cpp

@@ -1,21 +1,13 @@
 #include "pch.h"
 #include "Sound.h"
 
-#ifndef SDL_MIXER_VERSION_ATLEAST
-#define SDL_MIXER_VERSION_ATLEAST(X, Y, Z)   (SDL_MIXER_COMPILEDVERSION >= SDL_VERSIONNUM(X, Y, Z))
-#endif
-
 int Sound::num_channels;
 bool Sound::enabled_flag = false;
 int* Sound::TimeStamps = nullptr;
 
 bool Sound::Init(int channels, bool enableFlag)
 {
-#if SDL_MIXER_VERSION_ATLEAST(2, 0, 3)
-	Mix_Init(MIX_INIT_MID);
-#else
-    Mix_Init(MIX_INIT_FLUIDSYNTH);
-#endif
+	Mix_Init(MIX_INIT_MID_Proxy);
 	auto result = Mix_OpenAudio(MIX_DEFAULT_FREQUENCY, MIX_DEFAULT_FORMAT, 2, 1024);
 	SetChannels(channels);
 	Enable(enableFlag);

SpaceCadetPinball/pch.h

@@ -34,6 +34,14 @@
 #include "SDL.h"
 #include <SDL_mixer.h>
 
+// MIX_INIT_FLUIDSYNTH was renamed to MIX_INIT_MID in SDL_mixer v2.0.2
+constexpr int MIX_INIT_MID_Proxy =
+#if SDL_MIXER_PATCHLEVEL >= 2
+	MIX_INIT_MID;
+#else
+	MIX_INIT_FLUIDSYNTH;
+#endif
+
 //https://github.com/ocornut/imgui 7b913db1ce9dd2fd98e5790aa59974dd4496be3b
 #include "imgui.h"
 #include "imgui_internal.h"