pgsql: Allow callers to pass a missing_ok flag when opening a relation.

Allow callers to pass a missing_ok flag when opening a relation.

Since the names try_relation_openrv() and try_heap_openrv() don't seem
quite appropriate, rename the functions to relation_openrv_extended()
and heap_openrv_extended(). This is also more general, if we have a
future need for additional parameters that are of interest to only a
few callers.

This is infrastructure for a forthcoming patch to allow
get_object_address() to take a missing_ok argument as well.

Patch by me, review by Noah Misch.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/9abbed0629c862710bdc0f0dd3565e069ecab9da

Modified Files
--------------
src/backend/access/heap/heapam.c | 24 ++++++++++++++----------
src/backend/parser/parse_relation.c | 2 +-
src/include/access/heapam.h | 6 ++++--
src/pl/tcl/pltcl.c | 4 ++--
4 files changed, 21 insertions(+), 15 deletions(-)