Add static caching for Twig_Environment::getTemplateClass()
Added test case for issue #1143
fixed template_from_string when the template includes or extends other ones
fixed a bug in some unit tests (closes #1092)
fixed the filesystem loader cache when a template name exists in several namespaces
optimized the filesystem loader

* added a cache for templates that do not exist
* sped up Filesystem::exists() by avoiding the creation of exceptions
tweaked documentation about overloading existing filters, ... (closes #1094)
[ext] access static properties, fixed #1143

Twig extension access static properties wheras it should not
fixed versions in docs
merged branch tucksaun/fix-issue-1143 (PR #1147)

This PR was merged into the master branch.

Discussion
----------

Fix issue #1143

Commits
-------

5042159 [ext] access static properties, fixed #1143
dfc335f Added test case for issue #1143
updated CHANGELOG
merged branch fabpot/filesystem-optimizations (PR #1155)

This PR was merged into the master branch.

Discussion
----------

optimized the filesystem loader

* added a cache for templates that do not exist
* sped up Filesystem::exists() by avoiding the creation of exceptions

closes #1096

Commits
-------

d2b97b4 optimized the filesystem loader
merged branch fabpot/complex-template_from_string (PR #1154)

This PR was merged into the master branch.

Discussion
----------

fixed template_from_string when the template includes or extends other ones

This should fix #1134

Commits
-------

1b5bf91 fixed template_from_string when the template includes or extends other ones
merged branch Cottser/master (PR #1071)

This PR was merged into the master branch.

Discussion
----------

Add static caching for Twig_Environment::getTemplateClass()

Coming from http://drupal.org/node/1979290.

```
=== baseline-views-field-twig..views-field-twig-static-cache compared (517896dc57c6e..5178989df1d0f):

ct  : 116,895|115,892|-1,003|-0.9%
wt  : 478,367|474,349|-4,018|-0.8%
cpu : 449,530|444,639|-4,891|-1.1%
mu  : 17,447,208|17,453,200|5,992|0.0%
pmu : 17,658,176|17,664,136|5,960|0.0%
```

http://www.lionsad.de/xhprof-kit/xhprof/xhprof_html/?run1=517896dc57c6e&run2=5178989df1d0f&source=drupal-perf-cottser&extra=baseline-views-field-twig..views-field-twig-static-cache

We found that performance could be measurably improved when the same template is rendered multiple times in a request.

Commits
-------

4ae5385 Add static caching for Twig_Environment::getTemplateClass()
fixed CS
fixed template_from_string() cache side-effects
replaced usage of md5/sha1 by sha256
simplified code