pgsql: Add backtrace support for error reporting

Add backtrace support for error reporting

Add some support for automatically showing backtraces in certain error
situations in the server.  Backtraces are shown on assertion failure;
also, a new setting backtrace_functions can be set to a list of C
function names, and all ereport()s and elog()s from the mentioned
functions will have backtraces generated.  Finally, the function
errbacktrace() can be manually added to an ereport() call to generate a
backtrace for that call.

Authors: Peter Eisentraut, Álvaro Herrera
Discussion: https://postgr.es/m//5f48cb47-bf1e-05b6-7aae-3bf2cd01586d@2ndquadrant.com
Discussion: https://postgr.es/m/CAMsr+YGL+yfWE=JvbUbnpWtrRZNey7hJ07+zT4bYJdVp4Szdrg@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/71a8a4f6e36547bb060dbcc961ea9b57420f7190

Modified Files
--------------
configure                        |  61 +++++++++++++++++++-
configure.in                     |   4 ++
doc/src/sgml/config.sgml         |  26 +++++++++
src/backend/utils/error/assert.c |  13 +++++
src/backend/utils/error/elog.c   | 117 +++++++++++++++++++++++++++++++++++++++
src/backend/utils/misc/guc.c     |  85 ++++++++++++++++++++++++++++
src/include/pg_config.h.in       |   6 ++
src/include/utils/elog.h         |   3 +
src/include/utils/guc.h          |   2 +
9 files changed, 315 insertions(+), 2 deletions(-)