pgsql: Add postmaster -C option to query configuration parameters, and

Add postmaster -C option to query configuration parameters, and have
pg_ctl use that to query the data directory for config-only installs.
This fixes awkward or impossible pg_ctl operation for config-only
installs.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/aaa6e1def292cdacb6b27088898793b1b879fedf

Modified Files
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doc/src/sgml/ref/postgres-ref.sgml  |   14 +++++++
src/backend/main/main.c             |    1 +
src/backend/postmaster/postmaster.c |   15 +++++++-
src/backend/tcop/postgres.c         |    8 +++-
src/bin/pg_ctl/pg_ctl.c             |   72 +++++++++++++++++++++++++++++++---
5 files changed, 100 insertions(+), 10 deletions(-)