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/test_main.cpp

@@ -1,8 +1,10 @@
-#include <QTest>
-#include <QObject>
 
-#include "uritests.h"
+
 #include "paymentservertests.h"
+#include "uritests.h"
+
+#include <QObject>
+#include <QTest>
 
 // This is all you need to run all the tests
 int main(int argc, char *argv[])