Log Message:
www/*passenger: Update to 5.2.1.

- Fixes a regression from 5.1.11 that prevented Passenger from
  compiling on FreeBSD in some cases.
- Fixes a bounds issue in printing an error message that could occur
  in some cases when spawning a child process fails.
- Fixes a regression from 5.2.0 which prevented setting the max pool
  idle time to 0.
- Warns if using an incompatible compiler on macOS < 10.13.
- No longer uses Security Framework on macOS 10.13+. This will prevent
  further keychain warnings from appropriately compiled Passengers.
- Fixes warning on macOS about /proc/self access (excluded some code
  that was intended only for Linux).
- `passenger-install-nginx-module` now downloads the preferred Nginx
  version via https.
- [Apache] Fixes a regression from 5.2.0 that caused a crash on
  startup when no top-level ServerName is set.
- [Enterprise] Adds support for using RAM-based pricing on Heroku.