egl: Minor changes to the _EGLConfig interface.

Mainly to rename _eglAddConfig to _eglLinkConfig, along with a few clean
ups.
diff --git a/src/egl/drivers/dri2/egl_dri2.c b/src/egl/drivers/dri2/egl_dri2.c
index eb8996f..75aa29f 100644
--- a/src/egl/drivers/dri2/egl_dri2.c
+++ b/src/egl/drivers/dri2/egl_dri2.c
@@ -272,7 +272,7 @@
    if (conf != NULL) {
       memcpy(&conf->base, &base, sizeof base);
       conf->dri_config = dri_config;
-      _eglAddConfig(disp, &conf->base);
+      _eglLinkConfig(&conf->base);
    }
 
    return conf;