Add comment regarding __WIN32__ in SkyEye code

src/core/arm/dyncom/arm_dyncom_interpreter.cpp

@@ -34,6 +34,10 @@
 
 using namespace std;
 
+// __WIN32__ was never defined on MSVC, but it is on MinGW,
+// so we need to remove it.
+// #ifdefs to __WIN32__ are dead code and will not even compile
+// anymore, due to bank_defs.h missing.
 #ifdef _WIN32
 #undef __WIN32__
 #endif