Fix GLchar problem (OpenGL ES does not provide GLchar)

So building with newer headers from Mesa (9.1.4) or vendor
provided headers from Mali drivers was failing.
Better mali-drivers compatibility with eselect-opengl

Now we are correctly reporting that it a gles-only driver.
Also the soname hacks are reworked to fix some pkgconfig
related glitches on switching between xorg-x11 and mali.