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
optimized the filesystem loader

* added a cache for templates that do not exist
* sped up Filesystem::exists() by avoiding the creation of exceptions
[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
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Fix issue #1143

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

This PR was merged into the master branch.

Discussion
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fixed template_from_string when the template includes or extends other ones

This should fix #1134

Commits
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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
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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
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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
fixed filesystem loader when the name needs to be normalized
reverted optimizations done in the filesystem loader as it beaks BC
fixed two edge case bug in the filesystem loader

* fixed caching when two templates have the same template name but a different namespace
* fixed the error message when a template has a namespace
removed usage of deprecated classes in unit tests
removed usage of deprecated constants