Add create_sid to session_set_save_handler and SessionHandler

A lot of code already existed to allow a custom create_sid handler, but
lacked a specific implementation.

Therefore I have added a 7th (optional) argument
session_set_save_handler, to allow a user function to be supplied for
session id generation.

If a create_sid function is not supplied, the default function is
called in its absence to preserve backwards compatibility.

Likewise create_sid only added to SessionHandler class, and not the
interface to maintain backwards compatibility. If the result is not
overridden, the default is called.
Tests, fixes and optimisations

* Amended existing tests to cater for new functionality.
* Implemented fixes and optimisations recommended by NikiC
* Added create_sid to the registered interface. This was breaking
tests. It also now breaks BC for people implementing the interface
directly instead of extending the class.
Fixed bug bug #64713 Compilation warnings in finfo
Merge branch 'PHP-5.4' into PHP-5.5

* PHP-5.4:
  Fixed bug bug #64713 Compilation warnings in finfo
Merge branch 'PHP-5.5'

* PHP-5.5:
  Fixed bug bug #64713 Compilation warnings in finfo
updated libmagic.patch
Merge branch 'PHP-5.4' into PHP-5.5

* PHP-5.4:
  updated libmagic.patch
Merge branch 'PHP-5.5'

* PHP-5.5:
  updated libmagic.patch
Fix memory realted to #64726
Merge branch 'PHP-5.3' into PHP-5.4
Fixed bug #64726 (Segfault when calling fetch_object on a use_result and DB pointer has closed)
Merge branch 'PHP-5.4' into PHP-5.5
Update NEWS
Merge branch 'PHP-5.5'
Also fixed bug #64726 in 5.3
Merge branch 'PHP-5.3' into PHP-5.4
Merge branch 'PHP-5.4' into PHP-5.5
Merge branch 'PHP-5.5'
fix #64725, wrong res check
Merge branch 'PHP-5.5'

* PHP-5.5:
  fix #64725, wrong res check