pgsql: Add ddl_command_end support for event triggers.

Add ddl_command_end support for event triggers.

Dimitri Fontaine, with slight changes by me

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/841a5150c575ccd89e4b03aec66eeeefb21f3cbe

Modified Files
--------------
doc/src/sgml/event-trigger.sgml             |   93 +++++++++-
src/backend/commands/event_trigger.c        |  160 +++++++++++++---
src/backend/tcop/utility.c                  |  273 +++++++++++++++------------
src/backend/utils/cache/evtcache.c          |    2 +
src/include/commands/event_trigger.h        |    1 +
src/include/utils/evtcache.h                |    3 +-
src/test/regress/expected/event_trigger.out |    6 +-
src/test/regress/sql/event_trigger.sql      |    4 +
8 files changed, 390 insertions(+), 152 deletions(-)