Merge pull request #436 from pagespeed/jefftk-simplify-option-setting

options: refactor repeated code in option setting
static-handler: refactor to use write_handler_response

This fixes sending out the weak ETag for ngx_pagespeed_static/js_defer.hash.js,
and simplifies things somewhat for this code path.
It also adds a test for it.

Fixes https://github.com/pagespeed/ngx_pagespeed/issues/434
downstream-cache-test: don't hard code the port to 8051
Merge pull request #437 from pagespeed/oschaaf-downstream-cache-fix-test

downstream-cache-test: don't hard code the port to 8051
Merge pull request #435 from pagespeed/oschaaf-refactor-static-handler

static-handler: refactor to use write_handler_response
shutdown: fix a crash when shutting down a worker process

Remove the deferred cleanup, as in ngx_pagespeed the fetcher
is owned by the RewriteDriverFactory.

Fixes the backtrace pointing to
net_instaweb::RewriteDriverFactory::Deleter
at https://github.com/pagespeed/ngx_pagespeed/issues/367
Merge pull request #439 from pagespeed/oschaaf-shutdown-fix

shutdown: fix segfault when shutting down a worker process
keepalive-test: fix gzip accept encoding

We would send "Accept-Encoding:gzip" in the request headers. NGINX
would mark that as an invalid header, as it misses a space after ':'
Merge pull request #445 from pagespeed/oschaaf-fix-keepalive-test-gzip

keepalive-test: fix gzip accept encoding
- Refactor base fetch related functions.
- Add fix_headers filter