egl: Implement EGL_NOK_texture_from_pixmap

This extension allows a color buffer to be used for both rendering and
texturing.  EGL allows the use of color buffers of pbuffer drawables
for texturing, this extension extends this to allow the use of color
buffers of pixmaps too.

src/egl/main/egldisplay.h

@@ -47,6 +47,7 @@ struct _egl_extensions
    EGLBoolean KHR_gl_texture_3D_image;
    EGLBoolean KHR_gl_renderbuffer_image;
    EGLBoolean NOK_swap_region;
+   EGLBoolean NOK_texture_from_pixmap;
 
    char String[_EGL_MAX_EXTENSIONS_LEN];
 };