mesa: Rename API_OPENGL to API_OPENGL_COMPAT.

This should help avoid confusion now that we're using the gl_api enum
to distinguishing between core and compatibility API's.  The
corresponding enum value for core API's is API_OPENGL_CORE.

Acked-by: Eric Anholt <eric@anholt.net>
Acked-by: Matt Turner <mattst88@gmail.com>
Acked-by: Kenneth Graunke <kenneth@whitecape.org>

src/mesa/state_tracker/st_extensions.c

@@ -527,7 +527,7 @@ void st_init_extensions(struct st_context *st)
    ctx->Extensions.NV_texture_rectangle = GL_TRUE;
 
    ctx->Extensions.OES_EGL_image = GL_TRUE;
-   if (ctx->API != API_OPENGL)
+   if (ctx->API != API_OPENGL_COMPAT)
       ctx->Extensions.OES_EGL_image_external = GL_TRUE;
    ctx->Extensions.OES_draw_texture = GL_TRUE;