Any function of Lua log module would first evaluate the call stack,
and only then invoke the logger function -- even if the text is
then sent to /dev/null because log level is too low.

Short cut the log call in case the log level is low and the message
is muted.

Conflicts:
	src/iproto.cc

Conflicts:
	src/iproto.cc

When selecting the next buffer to flush, take into account not
just its size, but how much of it has already been flushed.
This saves a couple syscalls per connection per event loop.

Display how much memory is used by a fiber, and the total size.

1)removed atfork xlog resources freeing - they could be corrupted but xlog thread
2)snapshot.test now use pcall(box.snapshot) for deterministic code flow

Iproto + wal permission test case
Wal writer bug fix port from 1.6.6

remove unused config

fixed gh-731 : now every rtree has it's own matras instance that is destroyed with rtree, releasing all memory of tree instance

gh-613 replication conflict test cases

gh-613 after review fixes

microsleep for CRDT test case, test-run updated

CRDT fix