pgsql: Add an "events" system to libpq, whereby applications can get

Log Message:
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Add an "events" system to libpq, whereby applications can get callbacks that
enable them to manage private data associated with PGconns and PGresults.

Andrew Chernow and Merlin Moncure

Modified Files:
--------------
pgsql/doc/src/sgml:
libpq.sgml (r1.260 -> r1.261)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/libpq.sgml?r1=1.260&r2=1.261)
pgsql/src/interfaces/libpq:
Makefile (r1.166 -> r1.167)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/Makefile?r1=1.166&r2=1.167)
exports.txt (r1.19 -> r1.20)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/exports.txt?r1=1.19&r2=1.20)
fe-connect.c (r1.359 -> r1.360)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/fe-connect.c?r1=1.359&r2=1.360)
fe-exec.c (r1.197 -> r1.198)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/fe-exec.c?r1=1.197&r2=1.198)
libpq-fe.h (r1.142 -> r1.143)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/libpq-fe.h?r1=1.142&r2=1.143)
libpq-int.h (r1.131 -> r1.132)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/libpq-int.h?r1=1.131&r2=1.132)
pgsql/src/tools/msvc:
Install.pm (r1.30 -> r1.31)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/tools/msvc/Install.pm?r1=1.30&r2=1.31)

Added Files:
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pgsql/src/interfaces/libpq:
libpq-events.c (r1.1)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/libpq-events.c?rev=1.1&content-type=text/x-cvsweb-markup)
libpq-events.h (r1.1)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/libpq-events.h?rev=1.1&content-type=text/x-cvsweb-markup)