Passenger 6.0.1: fixes runaway CPU issue

Version 6.0.1 of the Passenger application server has been released. Most notably, this release fixes a startup issue when supporting generic apps.

Passenger 6, introduces Generic Language Support, or: the ability to support all and every arbitrary app.

Runaway CPU issue fixed

A GitHub issue submitted by @anamba, a long-time Passenger user excited to be able to use Passenger 6 for his Crystal applications. Experiencing a runaway CPU issue on Ubuntu 18.04 (Bionic), and with neither the Crystal app nor Passenger's error output being any help (even at log-level=7), anamba put together a demo with a Docker config. After a little back and forth we were able to reproduce the issue where ephemeral ports could be exhausted during the "Generic Language Support" startup handshake.

GH-2144 is now resolved.

Updates & improvements

Skips trying to set oom score in LXC container environments. Closes GH-2143.
Updated Ruby versions used in precompiled binaries (used for e.g. gem installs) to include 2.5.3, and 2.4.5 (removed: 2.4.4).
Bumps the preferred Nginx version to 1.15.8.
Updated various library versions used in precompiled binaries (used for e.g. gem installs):
- Curl: 7.62.0 -> 7.63.0
- Git: 2.19.2 -> 2.20.1
- Gnupg: 2.2.11 -> 2.2.12
- libassuan: 2.5.1 -> 2.5.2
- libgpg_error: 1.32 -> 1.33
- Ruby: 2.4.4 -> 2.4.5, + 2.5.3
- RubyGems: 2.7.6 -> 3.0.0

Installing 6.0.1

Please see the installation guide for advice on getting started with Passenger. Coming from a language other than Ruby, Python, Meteor or Node? Even if we didn't write a specific tutorial for your language, we made a generic guide that shows you the steps.