[PATCH] postgresql.conf.sample->postgresql.conf.sample.in

A patch for converting postgresql.conf.sample to
postgresql.conf.sample.in . This feature allows you to manage the
contents of postgresql.conf.sample at the configure phase.

Usage example:

./configure --enable-foo

configure.in:

foo_params=$(cat <<-END
foo_param1 = on
foo_param2 = 16
END
)
AC_SUBST(foo_params)

postgresql.conf.sample.in:

@foo_params@

postgresql.conf.sample:

foo_param1 = on
foo_param2 = 16

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