Add STAT_PLANS_DEBUG infrastructure

This infrastructure can be used to debug problems with pg_stat_plans
fingerprinting logic. When the macro STATS_PLAN_DEBUG is defined, Postgres will
print a low-level representation of each plan tree that is fingerprinted, as it
is fingerprinted.

Add documentation on how to debug problems with pg_stat_plans' fingerprinting
logic, including using this new infrastructure.
Merge pull request #18 from petergeoghegan/master

Add debugging infrastructure
Remove unused contact E-mail address
Merge pull request #19 from petergeoghegan/master

Remove unused e-mail address from documentation
Support for PostgreSQL 9.3.

Adjust ProcessUtility hooks to match new signature in PostgreSQL 9.3.
Merge pull request #21 from psoo/port93

Support for PostgreSQL 9.3.
Fix backend crash in case an empty search_path was set.

This could happen in case a database session has set a search_path
to a schema not accessible by the current role for example.
This results in an empty activeSearchPath list, which is returned by
fetch_search_path() as an empty list. Access in get_search_path_xor()
then causes a crash.

The best solution to this seems to also include any implicit search_path
members, too. This also seems to be a more correct definition in the sense
of a "stable" view when evaluating the plans later.
Merge pull request #24 from psoo/fix_get_search_path_xor

Fix backend crash in case an empty search_path was set.
catalog/pg_collation.h is only available in >= 9.1
Fix and extend description of debian package
Miscellaneous tweaks.

Update copyright year. Remove old e-mail address in pg_find_plans README.
Correct obsolete comment.
When explaining, verify query text

There are some scenarios in which it is possible for multiple calls to the
executor to occur at the same nesting level for the same query. This includes,
at the very least, when SQL functions are called.

As protection against the SQL function case in particular, but also as
insurance against other cases that may emerge, record the SQL text (EXPLAIN...
prefix and all) to be explained within pg_stat_plans_explain, and then verify
that it is consistent with the query descriptor sourceText indicated within
pgsp_ExecutorEnd().
Merge pull request #29 from petergeoghegan/fix_explain

When explaining, verify query text
Merge pull request #28 from petergeoghegan/master

Miscellaneous tweaks.
Merge pull request #26 from terrorobe/patch-2

Fix and extend description of debian package
Merge pull request #25 from terrorobe/patch-1

catalog/pg_collation.h is only available in >= 9.1
Fix oversight in last commit
Merge pull request #30 from petergeoghegan/master

Fix oversight in last commit