Updating trunk-tracking to be in sync with r3298.

Fixes to allow ngx_pagespeed trunk-tracking branch to compile and work with r3298 mod_pagespeed revision:
- Config fix to include path for critical_keys.pb.h.
- Make changes needed due to RewriteOptions refactoring done in https://code.google.com/p/modpagespeed/source/detail?r=3226
Merge pull request #440 from pagespeed/anupama-updates-to-trunk-tracking

Updating trunk-tracking to be in sync with r3298.