pgsql: Make pg_basebackup skip temporary statistics files.

Make pg_basebackup skip temporary statistics files.

The temporary statistics files don't need to be included in the backup
because they are always reset at the beginning of the archive recovery.
This patch changes pg_basebackup so that it skips all files located in
$PGDATA/pg_stat_tmp or the directory specified by stats_temp_directory
parameter.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/3e8554a54a95425e93fe49025ccda499a1a93173

Modified Files
--------------
contrib/pg_stat_statements/pg_stat_statements.c | 3 ++-
src/backend/replication/basebackup.c | 31 ++++++++++++++++++++++-
src/backend/utils/misc/guc.c | 2 +-
src/include/pgstat.h | 3 +++
4 files changed, 36 insertions(+), 3 deletions(-)