Tweak some wc.db query usages in preparation for changing
svn_wc__db_retract_parent_delete()'s behavior to keep
the moved to state valid.

No functional changes.

* subversion/libsvn_wc/wc-queries.sql
  (STMT_DELETE_NODE): Redefine with additional argument, as this name
    didn't explain the true behavior anyway.

  (STMT_DELETE_ALL_LAYERS): Rename to ...
  (STMT_DELETE_NODE_ALL_LAYERS): ... this, to document that it removes
    all layers of a node by its name.

* subversion/libsvn_wc/wc_db.c
  (svn_wc__db_retract_parent_delete): Implement logic in c that used to be
    performed in sqlite to allow handling other cases. Document what needs
    to be fixed. As this function is only used within sqlite transactions
    there is no measurable performance impact.

  (remove_node_txn,
   commit_node): Use STMT_DELETE_NODE_ALL_LAYERS instead of the old,
     but (identical) STMT_DELETE_NODE.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1538925 13f79535-47bb-0310-9956-ffa450edef68