[Sync-En] document the PHP 8.5 core language features and deprecations

[lacatoire]

Translation of php/doc-en#5824 (commit 4c352e6) and php/doc-en#5823 (commit cf7dcff): the PHP 8.5 core additions (type casts, closures and first-class callables in constant expressions, stack traces in fatal errors, Closure as a subtype of callable) and the PHP 8.5 deprecations (constant redeclaration, __debugInfo() returning null, incrementing non-numeric strings, binding closures across incompatible scopes, output inside an output handler), plus the new max_memory_limit INI setting. EN-Revision updated.

Both commits touch language/constants.xml, and the second is the later commit on it, so they cannot be split across PRs without check-en-revision failing.

Fixed a few defects in the files along the way: "cierre" was treated as feminine throughout bindto.xml and one of its paragraphs no longer matched the English, ob-start.xml had an example whose code searched for French strings that never appear in its own output, the increment page had a truncated first sentence and an echo that disagreed with the expected output, and there were two typos in callable.xml. Note that large parts of language/functions.xml are still untranslated upstream of this change; that is left as is.

Fixes: #1276
Fixes: #1278