Thread: pgsql: Minor fixes for the EXPLAIN reference page.

Log Message:
-----------
Minor fixes for the EXPLAIN reference page. Mention the fact that
EXPLAIN ANALYZE can sometimes be significantly slower than running
the same query normally, and make some minor markup improvements.

Modified Files:
--------------
    pgsql/doc/src/sgml/ref:
        explain.sgml (r1.39 -> r1.40)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/explain.sgml.diff?r1=1.39&r2=1.40)