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.
fix bug #61860: use USearch for searches, it does the right thing
small optimization
Fix #65108 (is_callable() triggers Fatal Error)

We have to check if the fcall info cache contains a pointer if we
use __call, otherwise we endup in a static lookup.
Merge branch 'PHP-5.5'

* PHP-5.5:
  Fix #65108 (is_callable() triggers Fatal Error)
Notify doc team BEFORE we release
Merge branch 'PHP-5.5'

* PHP-5.5:
  Notify doc team BEFORE we release
Fixed bug (is_callable() triggers Fatal Error)

This bug is also exists in 5.4, and previous fix by dsp is not complete
for __callStatic stituation, see test script
Merge branch 'PHP-5.4' into PHP-5.5

Conflicts:
	Zend/zend_API.c
Merge branch 'PHP-5.5' of git.php.net:php-src into PHP-5.5
Merge branch 'PHP-5.5'
- Fixed bug #61387 (NULL valued anonymous column causes segfault in odbc_fetch_array) patch by: Brandon Kirsch
Merge branch 'PHP-5.4' into PHP-5.5

* PHP-5.4:
  - Fixed bug #61387 (NULL valued anonymous column causes segfault in odbc_fetch_array) patch by: Brandon Kirsch
Merge branch 'PHP-5.5'

* PHP-5.5:
  - Fixed bug #61387 (NULL valued anonymous column causes segfault in odbc_fetch_array) patch by: Brandon Kirsch
- BFN
- Fixed bug #61594 (ext/session/mod_mm.c: missing free of ps_mm_instance) patch by: jlawall at hotmail dot com
Merge branch 'PHP-5.4' into PHP-5.5

* PHP-5.4:
  - Fixed bug #61594 (ext/session/mod_mm.c: missing free of ps_mm_instance) patch by: jlawall at hotmail dot com
  - BFN
Merge branch 'PHP-5.5'

* PHP-5.5:
  - Fixed bug #61594 (ext/session/mod_mm.c: missing free of ps_mm_instance) patch by: jlawall at hotmail dot com
  - BFN
Some tidy-ups: Don't mention Logo GUIDs in three places; mention
password_hash functionality; add some doc URLs for new features;
grammar & typos; formatting changes.