GUI-less build target bitcoind that links to wxBase and shouldn't need GTK,

split init and shutdown from ui.cpp into init.cpp,
support wxUSE_GUI=0
-- version 0.2.7

main.h

@@ -45,6 +45,8 @@ extern int64 nTransactionFee;
 extern CAddress addrIncoming;
 extern int fLimitProcessors;
 extern int nLimitProcessors;
+extern int fMinimizeToTray;
+extern int fMinimizeOnClose;