Teach Sqlite a bit of how we use our working copy database files, like that
we only have one true value in wc_id.

By adding this tiny bit of information Sqlite 3.8.0, 3.8.1 and the preview
of 3.8.2 use the intended query plans for our working copy queries, just
like Sqlite 3.7.12-3.7.19 already did without these hints.
(The older versions do use this information though!)

For more details on why this is important and how this works see
- the wc-metadata.sql patch
- http://www.sqlite.org/queryplanner-ng.html
- http://www.sqlite.org/fileformat2.html#stat1tab

And for reference also check the users@sqlite archive where Richard Hipp
recommends this approach for our current use of Sqlite.

* subversion/libsvn_wc/upgrade.c
  (svn_wc__upgrade_sdb): Call svn_wc__db_install_schema_statistics() after the
    final format bump.

* subversion/libsvn_wc/wc-metadata.sql
  (STMT_INSTALL_SCHEMA_STATISTICS): New statement.

* subversion/libsvn_wc/wc_db.c
  (svn_wc__db_install_schema_statistics): New function.

* subversion/libsvn_wc/wc_db.h
  (svn_wc__db_install_schema_statistics): New function.

* subversion/tests/libsvn_wc/wc-queries-test.c
  (schema_statements): Install the statistics.
  (parse_stat_data): New helper function.
  (test_schema_statistics): New test.
  (test_funcs): Add test_schema_statistics.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1542765 13f79535-47bb-0310-9956-ffa450edef68