Short circuit cleaning up reconciliation boundary structures.

The list of structures can grow very large, and cleaning up on each
reconciliation is a performance bottle neck.
Rename verbose ckpt to checkpoint, add some more messages to it.

The messages relate to the volume of data being written in checkpoints.
Don't maintain the per-size skiplist unless it's an element on the live
"avail" list.  The problem is we're holding the live system's spinlock
when updating the per-size skiplist, and that appears to be a bottleneck.
Reference #924.
Add a fast path for file extensions so we don't walk the list of
allocations for workloads where we already know we want to either
extend, or add an element after, the last element.  Ref #924.
*shrug*  Don't put an if/else inside the for loop, it's not needed and
it may help the compiler figure out the code motion.

Assert we never append an entry that's in the wrong place.
whitespace
Inline the block extension function, do a fast check for available
bytes before doing a search.
error: comparison between signed and unsigned integer expressions
[-Werror=sign-compare]
Merge pull request #923 from wiredtiger/verbose-checkpoint

Rename verbose ckpt to checkpoint, add some more messages to it.
Add max latency and min throughput settings. #926
Fix paren warning.
Use lprintf to exit, rather than an abort in wtperf.
Merge pull request #927 from wiredtiger/wtperf-debug

Add max latency and min throughput settings to wtperf. #926
Merge branch 'develop' into multiple-eviction-threads