Cleanup code using forward declarations.

Use misc methods of avoiding unnecesary header includes.
Replace int typedefs with int##_t from stdint.h.
Replace PRI64[xdu] with PRI[xdu]64 from inttypes.h.
Normalize QT_VERSION ifs where possible.
Resolve some indirect dependencies as direct ones.
Remove extern declarations from .cpp files.

src/base58.h

@@ -3,7 +3,6 @@
 // Distributed under the MIT/X11 software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-
 //
 // Why base-58 instead of standard base-64 encoding?
 // - Don't want 0OIl characters that look the same in some fonts and
@@ -15,14 +14,18 @@
 #ifndef BITCOIN_BASE58_H
 #define BITCOIN_BASE58_H
 
+#include "bignum.h"
+#include "chainparams.h"
+#include "hash.h"
+#include "key.h"
+#include "script.h"
+#include "uint256.h"
+
 #include <string>
 #include <vector>
 
-#include "chainparams.h"
-#include "bignum.h"
-#include "key.h"
-#include "script.h"
-#include "allocators.h"
+#include <boost/variant/apply_visitor.hpp>
+#include <boost/variant/static_visitor.hpp>
 
 static const char* pszBase58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";