NetPlay: add a Common/ENetUtil namespace

Move WakeupThread in it

Source/Core/Common/CMakeLists.txt

@@ -1,6 +1,7 @@
 set(SRCS BreakPoints.cpp
          CDUtils.cpp
          ColorUtil.cpp
+         ENetUtil.cpp
          FileSearch.cpp
          FileUtil.cpp
          GekkoDisassembler.cpp