egl: Implement EGL_NOK_swap_region

This extension adds a new function which provides an alternative to
eglSwapBuffers. eglSwapBuffersRegionNOK accepts two new parameters in
addition to those in eglSwapBuffers. The new parameters consist of a
pointer to a list of 4-integer blocks defining rectangles (x, y,
width, height) and an integer specifying the number of rectangles in
the list.

src/egl/main/egldisplay.h

@@ -46,6 +46,7 @@ struct _egl_extensions
    EGLBoolean KHR_gl_texture_cubemap_image;
    EGLBoolean KHR_gl_texture_3D_image;
    EGLBoolean KHR_gl_renderbuffer_image;
+   EGLBoolean NOK_swap_region;
 
    char String[_EGL_MAX_EXTENSIONS_LEN];
 };