pgsql-server: Restructure error handling as recently discussed.

Log Message:
-----------
Restructure error handling as recently discussed. It is now really
possible to trap an error inside a function rather than letting it
propagate out to PostgresMain. You still have to use AbortCurrentTransaction
to clean up, but at least the error handling itself will cooperate.

Modified Files:
--------------
pgsql-server/src/backend/bootstrap:
bootstrap.c (r1.189 -> r1.190)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/bootstrap/bootstrap.c.diff?r1=1.189&r2=1.190)
pgsql-server/src/backend/commands:
copy.c (r1.227 -> r1.228)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/commands/copy.c.diff?r1=1.227&r2=1.228)
portalcmds.c (r1.29 -> r1.30)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/commands/portalcmds.c.diff?r1=1.29&r2=1.30)
vacuum.c (r1.284 -> r1.285)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/commands/vacuum.c.diff?r1=1.284&r2=1.285)
pgsql-server/src/backend/postmaster:
bgwriter.c (r1.3 -> r1.4)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/postmaster/bgwriter.c.diff?r1=1.3&r2=1.4)
postmaster.c (r1.416 -> r1.417)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/postmaster/postmaster.c.diff?r1=1.416&r2=1.417)
pgsql-server/src/backend/storage/large_object:
inv_api.c (r1.103 -> r1.104)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/storage/large_object/inv_api.c.diff?r1=1.103&r2=1.104)
pgsql-server/src/backend/tcop:
postgres.c (r1.426 -> r1.427)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/tcop/postgres.c.diff?r1=1.426&r2=1.427)
pquery.c (r1.81 -> r1.82)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/tcop/pquery.c.diff?r1=1.81&r2=1.82)
pgsql-server/src/backend/utils/error:
elog.c (r1.143 -> r1.144)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/error/elog.c.diff?r1=1.143&r2=1.144)
pgsql-server/src/backend/utils/resowner:
README (r1.1 -> r1.2)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/resowner/README.diff?r1=1.1&r2=1.2)
resowner.c (r1.1 -> r1.2)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/resowner/resowner.c.diff?r1=1.1&r2=1.2)
pgsql-server/src/include/tcop:
tcopprot.h (r1.68 -> r1.69)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/tcop/tcopprot.h.diff?r1=1.68&r2=1.69)
pgsql-server/src/include/utils:
elog.h (r1.70 -> r1.71)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/utils/elog.h.diff?r1=1.70&r2=1.71)
pgsql-server/src/pl/plperl:
plperl.c (r1.47 -> r1.48)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/pl/plperl/plperl.c.diff?r1=1.47&r2=1.48)
pgsql-server/src/pl/plpgsql/src:
pl_comp.c (r1.77 -> r1.78)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/pl/plpgsql/src/pl_comp.c.diff?r1=1.77&r2=1.78)
pl_exec.c (r1.107 -> r1.108)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/pl/plpgsql/src/pl_exec.c.diff?r1=1.107&r2=1.108)
pgsql-server/src/pl/plpython:
plpython.c (r1.49 -> r1.50)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/pl/plpython/plpython.c.diff?r1=1.49&r2=1.50)
pgsql-server/src/pl/tcl:
pltcl.c (r1.86 -> r1.87)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/pl/tcl/pltcl.c.diff?r1=1.86&r2=1.87)

Removed Files:
-------------
pgsql-server/src/pl/plpython:
plpython.h
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/pl/plpython/plpython.h)