Do a runtime check of CRC hardware, if present, use CRC instructions.  refs #582
semantic sugar: whitespace, KNF, spelling checks.
Always cache the last key returned for use in scans.  Otherwise, we can do huge amounts of unnecessary work in __cursor_row_slot_return when scanning some pages.  This change speeds up test_backup03 by over 20% (by speeding up "wt dump").
Only futz with isolation in the top-level checkpoint code.

This fixes a bug introduced in the previous commit to txn_ckpt.c, and the code should not have been necessary anyway: metadata updates are single-threaded, so there can't be an uncommitted update, and if there are uncommitted updates when discarding a tree, we want to know about it.

refs #701
Merge branch 'develop' into scan-opt
minor cleanup, only assign to kb.{data,size} once.
Merge pull request #705 from wiredtiger/scan-opt

Always cache the last key returned for use in scans.
Use funcptr, inited from __wt_library_init.
Alphabetize and other cleanup.  refs #582
Merge pull request #702 from wiredtiger/hardware-cksum

Hardware cksum
Fix a comment, and a little whitespace tweaking, no real change.
ANSI C declaration, fix spelling.