This patch moves Odyssey from stream based write caching
to message driven. All write operations are delayed
and happen on a group of messages.
This removes necessity to do IO and wait for write completion during calls
from SSL_write() context. Write timings should behave more predictable now and
number of used syscalls should be also decreased.
This patch also simplifies caching management. All clients are simply
reusing cached messages without prolonged contention.
Several configuration options are no longer used:
pipeline, cache, cache_chunk