Problem: Injector thread consumes epoch events from event buffer (EB)
queue and writes to the Binlog. When the consumption gets slow, the EB
becomes full causing mysqld to shut down.

Fix: This EB-out-of memory(OOM) should be treated like inconsistent
epoch, by injecting a GAP event into the Binlog instead of crashing
mysqld.

The current event API is unable to get exceptional events like empty,
inconsistent or OOM. Use the new event API (nextEvent2, etc) in order
to get these events and handle them.

This patch series uses the 'new event API' for injector ndb, but not
for schema ndb. Reasons: S_ndb has not handled TE_INCONSISTENT by
writing gap epoch earlier. It gets fewer events compared to injector
ndb.

Reviewed by: Martin Skold <Martin.Skold@oracle.com>