P2075R6 philox_engine

[StephanTLavavej]

WG21-P2075R6 philox_engine
LWG-4134 Issue with Philox algorithm specification
LWG-4153 Fix extra "-1" for philox_engine::max()

Feature-test macro:

#define __cpp_lib_philox_engine 202406L

Note: We're focused on implementing the remaining library-only features in C++23. Until that's done, we will NOT be accepting PRs for C++26 features.

[MattStephanson]

Although a PR won't be accepted at this time, to avoid duplication of effort I'll announce that I'm working on it anyway because the topic interests me.