It works fine for me.
Some things I noticed while checking this:
1. postgresql contrib extensions should not be listed, and are working even without the patches. (This includes for example hstore, dblink,...
Did not test if it is problem if one adds these to the config though.
2. I had postgis actually missing, due to a missing use module, but there was no complaint, system reconfigure went just fine, but creating extension postgis did not work. Can we add some way to check if the list supplied is sane?
3. contrib extensions also work fine with the patches applied.
4. I did not test if it works if we have more than one extension, but it looks good.
If we have any other extension packaged, we could take a look.
5. Do you think we should add a test?
6. I got a warning that the first patch introduces whitespace errors on current master. Is that ok?