Factor out socket flag selection into GetBlockingFlagIfNeeded()

No real changes, just refactor wxProtocol ctor to use a new function
that can be reused elsewhere too.

src/common/protocol.cpp

@@ -65,9 +65,7 @@ wxIMPLEMENT_ABSTRACT_CLASS(wxProtocol, wxObject);
 wxProtocol::wxProtocol()
 #if wxUSE_SOCKETS
     // Only use non blocking sockets if we can dispatch events.
-    : wxSocketClient((wxIsMainThread() && wxApp::IsMainLoopRunning()
-                        ? wxSOCKET_NONE
-                        : wxSOCKET_BLOCK) | wxSOCKET_WAITALL)
+    : wxSocketClient(wxSocketClient::GetBlockingFlagIfNeeded() | wxSOCKET_WAITALL)
 #endif
 {
     m_lastError = wxPROTO_NOERR;