write set size limits controlled in provider library

Write set size limits must be controlled in provider library. Write set may overflow in:
* number of SQL statements appended in write set
* number of row keys appended in write set
* size of applying data passed into replication

If some of these write size limits is exceeded, provider library must return "size exceeded" error code, for corresponding wsrep call, and mysqld must cancel and rollback at least the current statement.

Change in wsrep API is specified in following lp bug:
lp:593419