pgsql: Include the current value of max_stack_depth in stack depth comp

Include the current value of max_stack_depth in stack depth complaints.

I'm mainly interested in finding out what it is on buildfarm machines,
but including the active value in the message seems like good practice
in any case.  Add the info to the HINT, not the ERROR string, so as not
to change the regression tests' expected output.

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=6736916f5f5a5f340aa20d4b27540764b5646585

Modified Files
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src/backend/tcop/postgres.c |    5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)