rbutil: Merge rbutil with utils folder.

rbutil uses several components from the utils folder, and can be
considered part of utils too. Having it in a separate folder is an
arbitrary split that doesn't help anymore these days, so merge them.

This also allows other utils to easily use libtools.make without the
need to navigate to a different folder.

Change-Id: I3fc2f4de19e3e776553efb5dea5f779dfec0dc21

utils/rbutilqt/test/stubs/stubs-compareversion.cpp

@@ -0,0 +1,31 @@
+
+#include "playerbuildinfo.h"
+#include "rbsettings.h"
+#include "rockboxinfo.h"
+
+// not used by the test, just to make things compile.
+QVariant RbSettings::value(RbSettings::UserSettings setting)
+{
+    (void)setting;
+    return QVariant();
+}
+
+
+// not used in the test. If used the test will crash!
+PlayerBuildInfo* PlayerBuildInfo::instance()
+{
+    return nullptr;
+}
+
+QVariant PlayerBuildInfo::value(PlayerBuildInfo::DeviceInfo item, QString target)
+{
+    (void)item;
+    (void)target;
+    return QVariant();
+}
+
+RockboxInfo::RockboxInfo(QString, QString)
+{
+}
+
+