QImage::constBits is qt >= 4.7 only

Based on Qt documentation, constBits seems to be a new 4.7-only  feature. 
http://harmattan-dev.nokia.com/docs/platform-api-reference/xml/daily-docs/libqt4/qimage.html#constBits

We should be able to use QImage::bits() since the argument type for glTexSubImage2D is const anyways, right ?
http://www.opengl.org/sdk/docs/man/xhtml/glTexSubImage2D.xml