pgsql: Don't override arguments set via options with positional argumen

Don't override arguments set via options with positional arguments.

A number of utility programs were rather careless about paremeters
that can be set via both an option argument and a positional
argument. This leads to results which can violate the Principal
Of Least Astonishment. These changes refuse to use positional
arguments to override settings that have been made via positional
arguments. The changes are backpatched to all live branches.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/1b37a8c3cc4f0615f80d6007e2bbd47c6bd7e1e3

Modified Files
--------------
src/bin/initdb/initdb.c | 7 +++++--
src/bin/scripts/clusterdb.c | 26 +++++++++++++++-----------
src/bin/scripts/createlang.c | 14 ++++++++++++--
src/bin/scripts/droplang.c | 14 ++++++++++++--
src/bin/scripts/reindexdb.c | 25 +++++++++++++++----------
src/bin/scripts/vacuumdb.c | 27 ++++++++++++++++-----------
6 files changed, 75 insertions(+), 38 deletions(-)