Add basic log buffering support. Not yet complete.
Move log slot initialization code back.

It didn't need to be moved, and was causing a bug.
Fix a race growing the log slot buffer.

A couple of other clean ups.
Use WT_CACHE_LINE_ALIGNMENT convention. #703
Various enhancements to consolidated logging:

* Complete the code that grows log buffers.
* Add a sleep in before slot close, allowing more writes to consolidate.
* Reduce the number of active slots to 1. This increases the amount of
* writes per slot, which improves throughput
Fix error handling in log slot initialization.

Also an optimization to log buffer grow code.
Fix error cleanup in log slot initialization.
Merge branch 'fine-grained-durability' into log-buffering

Manually resolved log.c
Conflicts:
	src/log/log.c
Change the sleep in log_slot_close to a yield.

Also increase the initial size for the log consolidation buffers.
Move log consolidation buffer grow to after updating write_lsn.
Add statistics to log buffering and general review cleanup.
Merge branch 'fine-grained-durability' into log-buffering
Merge branch 'fine-grained-durability' into log-buffering
Merge pull request #733 from wiredtiger/log-buffering

Log buffering