-Added threading support to windows port.
-Added portable socket code.
-Reworked gdb stub so it uses portable threading code.
-Reworked Netlink emulation. Now it's multi-threaded and should work beyond local and LAN connections.
-Changed Netlink debug logging so it's separate.
-A few CMakeLists.txt tweaks for SDL2 and winsock on windows.

git-svn-id: svn+ssh://svn.code.sf.net/p/yabause/code/trunk@3144 d7be59e3-070e-4b9a-85a1-4646befae34d