our sockets are always non-blocking anyhow so throw away all the code dealing with...

our sockets are always non-blocking anyhow so throw away all the code dealing with checking if they're blocking; also merge Unix/Win32 versions of connect() and accept() handling as they were almost identical except for the different checking of the return value which was factored out into a platform-specific GetLastError() function

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@57600 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775