Improve error message for unterminated string constants in vibe.web.i18n.
Fix crash in SSLContext.this().
Make all event drivers final and use the concrete derived type internally. See #675.

Avoids the need for many virtual function calls to the driver.
Move common timer logic to a separate TimerQueue struct.
Make most classes/methods final.

This is mostly an API change and not usually performance relevant.
Drop the "shared" from allocators and use a single lock layer instead of many single locks.

This is a preparation for full thread local allocators. Until this is done, there is still a single allocator hierarchy for all threads and this is protected by a single locking proxy at the top of the hierarchy.

See http://forum.rejectedsoftware.com/groups/rejectedsoftware.vibed/thread/17619/ for the performance bug that initiated this first step.
Fix compilation with VibeManualMemoryManagement.
Implement StreamOutputRange for buffered writing to output streams.
Perform some low-level optimization of the HTTP client.
Heavily reduce the size of HTTPServerRequest, resulting in a considerable speedup.

A lot of time was spent in emplace()/destroy() due to the sheer size of HTTPServerRequest (~88k).
Fix HTTP benchmark examples.

 - The server crashed with concurrent workload due to the match-tree based router rebuilding in multiple threads at the same time (all the code isn't really thread safe!)
 - Removed the hard-coded limit of 5k requests from the requester
 - Using a request concurrency level of 100 by default
 - Fixed an issue with incrementing a 64-bit token (is not an int)
Implement a small DNS cache to speed up multiple resoles of the same host name.
64-bit compile fix.
Perform a bit of low-level optimization.

Mainly reduces locking and (free list) allocation overhead.
Add documentation and status parameter to staticRedirect and HTTPServerResponse.redirect.
Deprecate implicit text block inside script/style tags. Fixes #228.
Avoid read-modify-write on shared counter (fixes compilation on DMD GIT master).
Bump version number to 0.7.20.
Merge branch '0.7.20'
Fix BSON custom serialization of const classes and fix the corresponding unit test. See #653.