Make sure the DEBUG flag is defined when building in debug mode

MSVC uses _DEBUG, unlike all of the other compilers, so we aren't
properly enabling/disabling varying bits of code that are dependent
on DEBUG being defined.

CMakeLists.txt

@@ -49,7 +49,7 @@ if ( MSVC )
 
     # Set always to static runtime
     set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} /MT")
-    set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /MTd")
+    set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /MTd /DDEBUG")
     if (CMAKE_BUILD_TYPE STREQUAL "Debug")
         set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreadedDebug")
         set(CMAKE_MSVC_RUNTIME_LIBRARY_FLAG "MTd")

src/util.h

@@ -41,6 +41,9 @@
 
 #include <cassert>
 
+#ifdef ASSERT
+#undef ASSERT
+#endif
 #define ASSERT(x) assert(x)
 #define DEBUG_MSG(...) fprintf(stderr, __VA_ARGS__)
 #define DEBUG_fputs fputs