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/test/uritests.h

@@ -1,8 +1,8 @@
 #ifndef URITESTS_H
 #define URITESTS_H
 
-#include <QTest>
 #include <QObject>
+#include <QTest>
 
 class URITests : public QObject
 {