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/qt/addresstablemodel.h

@@ -9,9 +9,10 @@
 #include <QStringList>
 
 class AddressTablePriv;
-class CWallet;
 class WalletModel;
 
+class CWallet;
+
 /**
    Qt model of the address book in the core. This allows views to access and modify the address book.
  */