Break dependency of init on wallet.

This required some code movement (what was CWalletTx::AcceptToMemoryPool
doing in main?), and adding a few explicit includes that used to be
implicit through init.h.

src/rpcdump.cpp

@@ -6,6 +6,7 @@
 #include <fstream>
 
 #include "init.h" // for pwalletMain
+#include "wallet.h"
 #include "bitcoinrpc.h"
 #include "ui_interface.h"
 #include "base58.h"