pgsql: Add a small cache of locks owned by a resource owner in Resource

Add a small cache of locks owned by a resource owner in ResourceOwner.

Back-patch 9.3-era commit eeb6f37d89fc60c6449ca12ef9e91491069369cb, to
improve the older branches' ability to cope with pg_dump dumping a large
number of tables.

I back-patched into 9.2 and 9.1, but not 9.0 as it would have required a
significant amount of refactoring, thus negating the argument that this
is by-now-well-tested code.

Jeff Janes, reviewed by Amit Kapila and Heikki Linnakangas.

Branch
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REL9_1_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/9b1b9446f563c85d1fe6bb8fca91a2608f3b9577

Modified Files
--------------
src/backend/storage/lmgr/lock.c | 150 ++++++++++++++++++++++-----------
src/backend/utils/resowner/resowner.c | 95 ++++++++++++++++++++-
src/include/storage/lock.h | 4 +-
src/include/utils/resowner.h | 5 ++
4 files changed, 202 insertions(+), 52 deletions(-)