pg_ctl infinite loop and memory leak

To reproduce:

1. initdb -D data
2. cat /dev/null > data/postgresql.conf
3. pg_ctl -w -D data start

I attached a quick patch that seems to do the trick. It appears that
fgets() will always return non-NULL if the size passed in is 1 (i.e.
maxlength in the caller is 0).

The patch also changes the same readfile() function in initdb.c. I
assume it's not a practical problem there, but it should be fixed.

Thanks to Corry Haines (chaines at truviso dot com) for reporting the
problem.

Regards,
    Jeff Davis