Corrected ORDINALITY column type.
Improve ilist.h's support for deletion of slist elements during iteration.

Previously one had to use slist_delete(), implying an additional scan of
the list, making this infrastructure considerably less efficient than
traditional Lists when deletion of element(s) in a long list is needed.
Modify the slist_foreach_modify() macro to support deleting the current
element in O(1) time, by keeping a "prev" pointer in addition to "cur"
and "next".  Although this makes iteration with this macro a bit slower,
no real harm is done, since in any scenario where you're not going to
delete the current list element you might as well just use slist_foreach
instead.  Improve the comments about when to use each macro.

Back-patch to 9.3 so that we'll have consistent semantics in all branches
that provide ilist.h.  Note this is an ABI break for callers of
slist_foreach_modify().

Andres Freund and Tom Lane
Add GET DIAGNOSTICS ... PG_CONTEXT in PL/PgSQL

This adds the ability to get the call stack as a string from within a
PL/PgSQL function, which can be handy for logging to a table, or to
include in a useful message to an end-user.

Pavel Stehule, reviewed by Rushabh Lathia and rather heavily whacked
around by Stephen Frost.
Merge branch 'ordinality' of github.com:davidfetter/returning_before_after into ordinality
Merge branch 'master' into ordinality