Getting it working with mod_pagespeed (r3061).

Updating trunk-tracking to compile and work with mod_pagespeed svn revision 3061 with 2 small modifications to serf_url_async_fetcher.cc to disable SERF_HTTPS_FETCHING.

Please note that anyone building mod_pagespeed from source will need to
a) edit serf_url_async_fetcher.h to change the line "#define SERF_HTTPS_FETCHING 1" to have 0.
b) edit serf_url_async_fetcher.cc to move the definition of "apr_status_t status = APR_SUCCESS;" on line 265 to be inside the "#if SERF_HTTPS_FETCHING" block (in order to avoid a compilation error for psol/mod_pagespeed).

Highlights of this change:

1) Propagating renaming changes related to
  a) Furious -> Experiment
  b) ModPagespeed -> PageSpeed.
2) UrlPollableAsyncFetcher going away.
3) RewriteOptions now requiring a ThreadSystem parameter for construction.
4) Removing client_property_cache references and usages (since this was removed from mod_pagespeed).
5) Propagating beacon construction changes (where POST requests can now carry the url query param in the request).
6) General fixes for API/test breakages in statistics_logger, fallback property page cache,
Merge pull request #396 from pagespeed/anupama-update-trunk-tracking

Getting it working with mod_pagespeed (r3061).
Merge branch 'master' into trunk-tracking
Fix paths for files moved from apache/ to system/
caching: support for proxy_cache

Add support for proxy_cache integration with pagespeed with:

a) Handling cache-hit-header to bypass content handling by pagespeed.
b) pagespeed_test_conf.template with the proxy_cache configuration blocks.
c) System tests for checking hit and miss headers and purge requests.
d) Checking for proxy_cache_purge module during start-up for tests.

Squash-merge of Anupama's #404
Add CFLAGS to fix OpenSSL linker error.
Use SystemRewriteDriverFactory::InitStats instead of RewriteDriverFactory::InitStats
Fix add_instrumentation test.
Remove unnecessary cc sources from config.
Revert removing system/ cc files, as that causes linker errors.
Fix paths for files moved from apache/ to system/
Add CFLAGS to fix OpenSSL linker error.
Use SystemRewriteDriverFactory::InitStats instead of RewriteDriverFactory::InitStats
Fix add_instrumentation test.
Remove unnecessary cc sources from config.
Revert removing system/ cc files, as that causes linker errors.
Merge branch 'jud-trunk-tracking' of https://github.com/pagespeed/ngx_pagespeed into jud-trunk-tracking
Merge pull request #405 from pagespeed/jud-trunk-tracking

Fix build errors with trunk
Updating trunk-tracking against PSOL r3130.

Small fix for compilation error caused due to removal of all synchronous fetchers in r3128.
Merge pull request #407 from pagespeed/anupama-updates-to-trunk-tracking

Updating trunk-tracking against PSOL r3130.