pgsql: Add large object functions catering to SQL callers.

Add large object functions catering to SQL callers.

With these, one need no longer manipulate large object descriptors and
extract numeric constants from header files in order to read and write
large object contents from SQL.

Pavel Stehule, reviewed by Rushabh Lathia.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/c50b7c09d852b6dc292bf24c72a0ffcac6cb2cab

Modified Files
--------------
doc/src/sgml/func.sgml                       |    3 +-
doc/src/sgml/lobj.sgml                       |   78 ++++++++++++-
src/backend/libpq/be-fsstubs.c               |  151 ++++++++++++++++++++++++++
src/include/catalog/catversion.h             |    2 +-
src/include/catalog/pg_proc.h                |    9 ++
src/include/libpq/be-fsstubs.h               |    5 +
src/test/regress/input/largeobject.source    |   21 ++++
src/test/regress/output/largeobject.source   |   50 +++++++++
src/test/regress/output/largeobject_1.source |   50 +++++++++
9 files changed, 362 insertions(+), 7 deletions(-)