Widget applications non-functional on certain embedded systems

The backingstore in eglfs uses GL_REPEAT. This cannot work for non-power-of-two sizes on systems where the OpenGL implementation does not support NPOT textures (and GL_REPEAT on them)

This results in not rendering widget windows on such embedded systems at all.

This can be fixed easily in eglfs since the use of GL_REPEAT originates from some old restrictions in QOpenGLTextureBlitter which have been since lifted.