Remove unneeded string copy.
Allow to set ''(empty string values) internal/input/output_encoding for better compatibility. i.e. Runtime INI value changes.
More compliance to the RFC. Improve/add encoding handling tests. i.e. Rather than set encoding automagic way, detect it.
Merge branch 'PHP-5.6'

* PHP-5.6:
  Remove unneeded string copy. Allow to set ''(empty string values) internal/input/output_encoding for better compatibility. i.e. Runtime INI value changes. More compliance to the RFC. Improve/add encoding handling tests. i.e. Rather than set encoding automagic way, detect it.