due to a typo, we end up trying to consume the *expected* amount of qids, but the walk could be shorter.

In particular it's important not to die if the first component can't be walked for any reason!

don't write more than fetched. The code wrote up to sizeof(buf), but it may try to write more than the data sent, which is r (<= sizeof(buf)).

while here also delete the two remaining makefiles from before the -portable merge.

fixes `make distcheck'. it's so GNU to not ship manpages by default :/

since we may want to spawn other programs, mark every file descriptor as cloexec. Fortunately, we don't end up opening many of them!

The `page' command fetches a file and displays it using less(1). To do this, refactor fetch_fid to accept a file descriptor and add a spawn utility function.