pgsql: Make get_stack_depth_rlimit() handle RLIM_INFINITY more sanely.

Make get_stack_depth_rlimit() handle RLIM_INFINITY more sanely.

Rather than considering this result as meaning "unknown", report LONG_MAX.
This won't change what superusers can set max_stack_depth to, but it will
cause InitializeGUCOptions() to set the built-in default to 2MB not 100kB.
The latter seems like a fairly unreasonable interpretation of "infinity".
Per my investigation of odd buildfarm results as well as an old complaint
from Heikki.

Since this should persuade all the buildfarm animals to use a reasonable
stack depth setting during "make check", revert previous patch that dumbed
down a recursive regression test to only 5 levels.

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=dd1c781903811416db4e03383a4cb0bfc8cfac40

Modified Files
--------------
src/backend/tcop/postgres.c           |   12 ++++++++----
src/backend/utils/misc/guc.c          |    4 ++--
src/test/regress/expected/plpgsql.out |    2 +-
src/test/regress/sql/plpgsql.sql      |    2 +-
4 files changed, 12 insertions(+), 8 deletions(-)