pgsql: Add more temporary code to record stack usage at server process

Add more temporary code to record stack usage at server process exit.

After a look at preliminary results from commit 88cf37d2a86d5b66,
I realized it'd be a good idea to spew out the maximum depth measurement
seen by check_stack_depth.  So add some quick-n-dirty code to do that.
Like the previous commit, this will be reverted once we've gathered
a set of buildfarm runs with it.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/ea9c4a16d5ad88a1d28d43ef458e3209b53eb106

Modified Files
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src/backend/storage/ipc/ipc.c | 12 ++++++++++++
src/backend/tcop/postgres.c   | 12 ++++++++++++
2 files changed, 24 insertions(+)