Fix wxSocket::WaitForAccept() in worker thread.

This was broken because Select() never returned wxSOCKET_CONNECTION_FLAG which
is supposed to be set when a connection is accepted.

Closes #15669.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@75211 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -574,6 +574,10 @@ Major new features in this release
 3.0.1: (released 2014-xx-xx)
 ----------------------------
 
+All:
+
+- Fix wxSocket::WaitForAccept() in non-main thread (Hajo Kirchhoff).
+
 All (GUI):
 
 - Fix crash when setting invalid label ending with "&" (ZaneUJi).