Make sure Windows builds don't get min and max macros defined from WinDef.h.

Originally committed to SVN as r4957.

aegisub/src/agi_pre.h

@@ -115,7 +115,6 @@
 #include <windows.h>
 #include <objbase.h>
 #include <mmsystem.h>
-//#include <process.h> // Currently only used in audio_player_dsound2.cpp
 
 #else
 

aegisub/src/config.h

@@ -2,6 +2,12 @@
 
 #ifdef _WIN32
 
+// Define min and max macros to identity.
+// This will prevent WinDef.h defining them to functions, which prevents
+// using std::min and std::max.
+#define min min
+#define max max
+
 // Windows specific settings
 #include "config/config_windows.h"