Properly handle the return values for the ignored blocks
Merge remote branch 'origin/master'

Conflicts:
	code/Model/Backend/Local.php
	js/fpc-prototype.js
Always encode 'blocks' as a JSON object.
Update overridden blocks with upstream from Magento 1.8.1.0
Add back X-Diehard: HIT header for Local backend on cache hit.
Add mention of sample implementation. Fix a few bugs.

- Use span instead of div for block injection (for compatibility with
containers that may only contain inline elements).
- Prevent httpResponseSendBefore observer when used in context of a
dynamic block replacement of a cache hit.