Decided to keep the strong_ordering semantics, as user code is very
much guaranteed to rely on it.
Update the docs.
[ChangeLog][Potentially Source-Incompatible Changes] Made several
operators (relational, QDebug streaming, etc) hidden friends. This may
break code that calls these operators a) with types that require
implicit conversion on the arguments, or b) using member-function
syntax (lhs.operator<(rhs)). The backwards-compatible fix for (a) is
to make at least one of the argument's implicit conversions
explicit. For (b), use infix notation (lhs < rhs).
[ChangeLog][EDITORIAL] Replace all "Potentially Source-Incompatible
Changes" items that mention making operators hidden friends with the
catch-all one from the QPersistentModelIndex change.
Fixes: QTBUG-117660
Change-Id: I8175af5e2cb3c77e7486e972630b9410b3a0896c
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
cbda958352