Parsing config files in a directory

Per discussion at the developer meeting back in Ottawa, attached is an
initial patch that implements reading a directory of configuration
files instead of just one. The idea being that something like a tuning
tool, or pgadmin, for example can drop and modify files in this
directory instead of modifying the main config file (which can be very
hard to machine-parse). The idea is the same as other software like
apache that parses multiple files.

Files are parsed in alphabetical order so it's predictable, and you
can make sure some files override others etc.

Comments, before I go do the final polishing? :-)

--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/