Add wsrep_size_exceeded error code

[Seppo Jaakola]

Add new wsrep_status enumeration to signal if replicator provider library cannot handle such large request. Suggested enumeration is: WSREP_SIZE_EXCEEDED.

Require following wsrep calls to return WSREP_SIZE_EXEEDED:
    append_data/pre_commit - if passed replication data buffer is too large for replication system
    append_query - if too many SQL statements were appended in transaction's write set
    append_row_key - if too many row key values were appended in transaction's write set

[Alex Yurchenko (ayurchen)]

Seppo, shall this be dead?

[Alex Yurchenko (ayurchen)]

Pushed in r65