pgsql: Add query text to auto_explain output.

Log Message:
-----------
Add query text to auto_explain output.

Still to be done: fix docs and fix regression failures under auto_explain.

Modified Files:
--------------
    pgsql/contrib/auto_explain:
        auto_explain.c (r1.12 -> r1.13)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/auto_explain/auto_explain.c?r1=1.12&r2=1.13)
    pgsql/src/backend/commands:
        explain.c (r1.202 -> r1.203)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/explain.c?r1=1.202&r2=1.203)
    pgsql/src/include/commands:
        explain.h (r1.45 -> r1.46)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/commands/explain.h?r1=1.45&r2=1.46)