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/leveldbwrapper.h

@@ -7,11 +7,11 @@
 
 #include "serialize.h"
 #include "util.h"
-
-#include <leveldb/db.h>
-#include <leveldb/write_batch.h>
+#include "version.h"
 
 #include <boost/filesystem/path.hpp>
+#include <leveldb/db.h>
+#include <leveldb/write_batch.h>
 
 class leveldb_error : public std::runtime_error
 {