[REG] Broken font rendering in embedded widgets when using OpenGL paint engine

On Windows and Linux, some font rendering in embedded widgets is broken when using the QWindowsXPStyle, QWindowsVistaStyle, QMotifStyle or QCdeStyle, with the OpenGL paint engine. Some text appear "less" antialiased or even aliased, or as chunks of black boxes (see attached screenshot pad_navigator_example_qt-4.6.1.jpg).

When this issue occurs, the following is printed to the console:

QGLShader::compile: "0(4) : error C1038: declaration of "textureCoords" conflicts with previous declaration at 0(4)"

This can be reproduced by running the padnavigator example with the above mentioned styles and flipping the pad.

This is a regression from Qt 4.6.0 (see screenshots demonstrating difference between Qt 4.6.0 and Qt 4.6.1).