Put all custom converters inside Shiboken namespace.

PySide/QtCore/qvariant_conversions.h

@@ -29,6 +29,7 @@ struct QMetaTypeId< PyObjectHolder >
 };
 QT_END_NAMESPACE
 
+namespace Shiboken {
 // all types are convertible to QVariant
 inline bool Converter<QVariant>::isConvertible(PyObject* pyobj)
 {
@@ -81,3 +82,4 @@ inline QVariant Converter<QVariant>::toCpp(PyObject* pyobj)
         return QVariant(typeCode, reinterpret_cast<SbkBaseWrapper*>(pyobj)->cptr);
     }
 }
+}