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.
Merge with MPS trunk as of 2003-07-19

This has 2 families of changes:
- Port to changes in PropertyCache API
- Update to a MapProxyDomain test.
Merge pull request #444 from morlovich/morlovich-trunk-tracking-20130719

trunk-tracking: merge with MPS trunk as of 2003-07-19
System test changes to align with latest mod_pagespeed trunk.
Merge pull request #458 from pagespeed/jud-trunk-tracking

Trunk tracking updates
merge commit
Merge branch 'master' into trunk-tracking
trunk-tracking: in_place_resource_recorder changes
trunk-tracking: adjust for big changes from r3366

SystemRewriteDriverFactory was expanded by r3366 to do a lot of what
NgxRewriteDriverFactory used to have to do.  Take advantage of this and
simplifiy our code.
trunk-tracking: update apache_system_test for minor changes in r3369 and r3374
Merge pull request #469 from pagespeed/jefftk-update-trunk-tracking

trunk-tracking: take advantage of new functionality in system/
Merge branch 'master' into trunk-tracking
trunk-tracking: update to r3402

Adjust for fetchers and options that moved from apache/ to system/ in r3390.

Use AllocateFetcher() hook from r3402 to put the native fetcher into the fetcher
map maintained by the SystemRewriteDriverFactory.
Removing redundant X-Cache header handling.

X-Cache handling is not needed because the pagespeed server never gets to see
a request with X-Cache header added by its downstream cache. X-Cache headers
are only to be added in responses served out of the downstream cache for debugging
purposes only. This piece of deleted code was also conflicting with X-Cache
headers present on upstream caches (wrt pagespeed) and hence not optimizing responses
that happened to carry this header.

(More details are present in https://github.com/pagespeed/ngx_pagespeed/issues/488)
Merge pull request #490 from pagespeed/new-trunk-tracking-rotation

Removing redundant X-Cache header handling.
Merge pull request #480 from pagespeed/jefftk-update-trunk-tracking

Adjust for fetchers and options that moved from apache/ to system/ in r3390
Merge branch 'master' into trunk-tracking
trunk-tracking: update to r3448 from r3403

As of r3447 ServerContext::ChildInit is now in system/, which means we can
delete a lot of code.

DangerFetchFromUnknownHosts and FetchWithGzip are now handled by RewriteOptions.

ServerContext now needs a hostname and port, but we don't have one so we
hackishly provide a different unique id.
Merge pull request #494 from pagespeed/jefftk-update-trunk-tracking

trunk-tracking: update to r3448 from r3403