pgsql-server: Another minor tweak to psql startup: set the default

Log Message:
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Another minor tweak to psql startup: set the default values for the PROMPT1,
PROMPT2 and PROMPT3 variables before we read any of the settings specified
via the user on the command-line or in psqlrc, so that the latter can
override the former. Per original patch from Ingo van Lil, simpler fix
suggested by Tom Lane.

Modified Files:
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    pgsql-server/src/bin/psql:
        startup.c (r1.102 -> r1.103)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/bin/psql/startup.c.diff?r1=1.102&r2=1.103)