Fix Cygwin 1.7 build.

Avoid using Cygwin sockets as our code assumes that we use WinSock API under
Windows currently (this might change in the future) by defining
__USE_W32_SOCKETS.

Use new, safer and more efficient cygwin_conv_path() function.

Use t_str() instead of fn_str() with Windows API taking file names, under
Cygwin they are different and using fn_str() is incorrect.

A few other minor fixes.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65057 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/evtloop.h

@@ -17,7 +17,7 @@
 
 // TODO: implement wxEventLoopSource for MSW (it should wrap a HANDLE and be
 //       monitored using MsgWaitForMultipleObjects())
-#if defined(__WXOSX__) || defined(__UNIX__)
+#if defined(__WXOSX__) || (defined(__UNIX__) && !defined(__CYGWIN__))
     #define wxUSE_EVENTLOOP_SOURCE 1
 #else
     #define wxUSE_EVENTLOOP_SOURCE 0
@@ -310,7 +310,7 @@ protected:
 #endif // wxUSE_GUI
 
 // include the header defining wxConsoleEventLoop for Unix systems
-#if defined(__UNIX__)
+#if defined(__UNIX__) && !defined(__CYGWIN__)
 #include "wx/unix/evtloop.h"
 #endif