src/corelib/globa/qconfig.h requires QT_NO_DEBUG to be defined, behavior inconsistent from rest of Qt

As of 4.7.0 beta 2, src/corelib/global/qconfig.h depends on QT_NO_DEBUG having a numerical value. This differs from the way QT_NO_DEBUG is used throughout the rest of Qt, where the check is to see if QT_NO_DEBUG is defined. These behaviors are incompatible with each other: if you wanted to enable debugging, qconfig.h would require you to "#define QT_NO_DEBUG 0", but then "#ifdef QT_NO_DEBUG" would return true - in other words, there would be no way to enable debugging.