sqlite: Improve error messages by including the sqlite numeric error code.
(At this time, we do not enable sqlite3_extended_result_codes().)

* subversion/libsvn_subr/sqlite.c
  (SQLITE_ERR, SQLITE_ERR_MSG, exec_sql2, svn_sqlite__step, init_sqlite, 
   internal_open): Include the sqlite numeric error code in the error string.
  (close_apr): Leave a marker where we discard the specific sqlite numeric
      error code.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1446410 13f79535-47bb-0310-9956-ffa450edef68