Optimized hash extract of {n}.field for PHP 5.5+
Since PHP 5.3 the variable is no longer copied

Removing the reference makes the code faster.
Improved Hash::get() performance

Calling Hash::get() with just one key is a very rare, since you can do $data[$key] directly. Just by adding this check it decreases the performance in about 15%.
Avoiding loops for Hash::get() up to 3 levels

Lots of configs and read do not use very deep levels to read. Having the switch to avoid loops can increase the performance in about 30%.
Merge pull request #4532 from jrbasso/3.0-hash-performance

3.0 Hash get/extract performance improvements