Document the PHP 8.5 core deprecations and max_memory_limit

[lacatoire]

Documents six PHP 8.5 core changes still marked Todo on the 8.5 documentation tracker.

• max_memory_limit INI setting — PHP 8.5 Documentation Tracker (view)
• Constant redeclaration deprecated — PHP 8.5 Documentation Tracker (view)
• Increment on non-numeric strings deprecated — PHP 8.5 Documentation Tracker (view)
• Returning null from __debugInfo() deprecated — PHP 8.5 Documentation Tracker (view)
• Closure binding deprecations on Closure::bind() and Closure::bindTo() — PHP 8.5 Documentation Tracker (view)
• Producing output within a user output handler deprecated — PHP 8.5 Documentation Tracker (view)

Wording follows the PHP 8.5 UPGRADING notes; each entry was checked against PHP 8.5.4.