Add Debug compile flag if we're building in debug mode.

CMakeLists.txt

@@ -42,6 +42,10 @@ if (WINDOWS)
     add_compile_options(-m64)
 endif (WINDOWS)
 
+if (CMAKE_BUILD_TYPE MATCHES "Debug")
+    ADD_DEFINITIONS(-DDEBUG)
+endif()
+
 set(LINKS)
 if (NOT WINDOWS AND PRETTYTRACES)
     set(LINKS ${LINKS} -ldw)