Inconsistency in postgresql.conf

I notice that we use '(none)' as a default for external_pid_file, while
other default no-value settings in the file are ''.  The attached patch
changes this.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +
commit b214e05827399ad320674b7d1d10979ada7f3e30
Author: Bruce Momjian <bruce@momjian.us>
Date:   Sat Oct 1 12:00:33 2011 -0400

    change 'none' default.

diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
new file mode 100644
index a18f14a..b2f8239
*** a/src/backend/utils/misc/postgresql.conf.sample
--- b/src/backend/utils/misc/postgresql.conf.sample
***************
*** 46,52 ****
                      # (change requires restart)

  # If external_pid_file is not explicitly set, no extra PID file is written.
! #external_pid_file = '(none)'        # write an extra PID file
                      # (change requires restart)


--- 46,52 ----
                      # (change requires restart)

  # If external_pid_file is not explicitly set, no extra PID file is written.
! #external_pid_file = ''        # write an extra PID file
                      # (change requires restart)