pgsql: Add lo_truncate() to backend and libpq for large object

Log Message:
-----------
Add lo_truncate() to backend and libpq for large object truncation.

Kris Jurka

Modified Files:
--------------
pgsql/doc/src/sgml:
lobj.sgml (r1.44 -> r1.45)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/lobj.sgml.diff?r1=1.44&r2=1.45)
pgsql/src/backend/libpq:
be-fsstubs.c (r1.85 -> r1.86)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/libpq/be-fsstubs.c.diff?r1=1.85&r2=1.86)
pgsql/src/backend/storage/large_object:
inv_api.c (r1.122 -> r1.123)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/large_object/inv_api.c.diff?r1=1.122&r2=1.123)
pgsql/src/include/catalog:
pg_proc.h (r1.446 -> r1.447)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h.diff?r1=1.446&r2=1.447)
pgsql/src/include/libpq:
be-fsstubs.h (r1.28 -> r1.29)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/libpq/be-fsstubs.h.diff?r1=1.28&r2=1.29)
pgsql/src/include/storage:
large_object.h (r1.36 -> r1.37)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/large_object.h.diff?r1=1.36&r2=1.37)
pgsql/src/interfaces/libpq:
exports.txt (r1.14 -> r1.15)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/exports.txt.diff?r1=1.14&r2=1.15)
fe-lobj.c (r1.61 -> r1.62)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/fe-lobj.c.diff?r1=1.61&r2=1.62)
libpq-fe.h (r1.135 -> r1.136)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/libpq-fe.h.diff?r1=1.135&r2=1.136)
libpq-int.h (r1.118 -> r1.119)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/libpq-int.h.diff?r1=1.118&r2=1.119)
pgsql/src/test/regress/input:
largeobject.source (r1.1 -> r1.2)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/input/largeobject.source.diff?r1=1.1&r2=1.2)
pgsql/src/test/regress/output:
largeobject.source (r1.1 -> r1.2)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/output/largeobject.source.diff?r1=1.1&r2=1.2)