Refactor out translation.h

This is a prerequisite for introducing bilingual error messages.
Note: #includes are arranged by clang-format-diff.py script.

src/bitcoin-wallet.cpp

@@ -9,10 +9,12 @@
 #include <chainparams.h>
 #include <chainparamsbase.h>
 #include <logging.h>
-#include <util/system.h>
 #include <util/strencodings.h>
+#include <util/system.h>
+#include <util/translation.h>
 #include <wallet/wallettool.h>
 
+#include <functional>
 #include <stdio.h>
 
 const std::function<std::string(const char*)> G_TRANSLATION_FUN = nullptr;