pgsql: Prevent auto_explain from changing the output of a user's EXPLAI

Prevent auto_explain from changing the output of a user's EXPLAIN.

Commit af7914c6627bcf0b0ca614e9ce95d3f8056602bf, which introduced the
EXPLAIN (TIMING) option, for some reason coded explain.c to look at
planstate->instrument->need_timer rather than es->timing to decide
whether to print timing info. However, the former flag might get set
as a result of contrib/auto_explain wanting timing information. We
certainly don't want activation of auto_explain to change user-visible
statement behavior, so fix that.

Also fix an independent bug introduced in the same patch: in the code
path for a never-executed node with a machine-friendly output format,
if timing was selected, it would fail to print the Actual Rows and Actual
Loops items.

Per bug #10404 from Tomonari Katsumata. Back-patch to 9.2 where the
faulty code was introduced.

Branch
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REL9_3_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/0266a9c78139d0f0d64dc1c440e60b8f30172046

Modified Files
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src/backend/commands/explain.c | 27 ++++++++++++++++-----------
1 file changed, 16 insertions(+), 11 deletions(-)