OpenGL: Add finer-grained functionality checks for NPOT textures

OpenGL: Add finer-grained functionality checks for NPOT textures

The GL_IMG_texture_npot extension only provides partial support for
npot textures in that it allows use of npot textures but it does not
support the GL_REPEAT texture mode (needed for tiling fill modes in the
QQ2 image element).

Adding this new finer-grained feature check allows QQ2 to still use npot
textures where GL_REPEAT is not needed with only the IMG extension
present.

A follow-up commit will make a check for this in qtdeclarative.

Change-Id: Iff3dbdb955fb334d9e32f3abd49e90ff0ed9836c
Reviewed-by: Gunnar Sletta <gunnar.sletta@nokia.com>