pgsql: In the stats test, delay for the stats collector to catch up

Log Message:
-----------
In the stats test, delay for the stats collector to catch up using a
function that actually sleeps, instead of busy-waiting.  Perhaps this
will resolve some of the intermittent stats failures we keep seeing.

Modified Files:
--------------
    pgsql/src/test/regress/expected:
        stats.out (r1.4 -> r1.5)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/stats.out.diff?r1=1.4&r2=1.5)
    pgsql/src/test/regress/input:
        create_function_1.source (r1.14 -> r1.15)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/input/create_function_1.source.diff?r1=1.14&r2=1.15)
    pgsql/src/test/regress/output:
        create_function_1.source (r1.25 -> r1.26)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/output/create_function_1.source.diff?r1=1.25&r2=1.26)
    pgsql/src/test/regress:
        regress.c (r1.62 -> r1.63)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/regress.c.diff?r1=1.62&r2=1.63)
    pgsql/src/test/regress/sql:
        stats.sql (r1.2 -> r1.3)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/stats.sql.diff?r1=1.2&r2=1.3)