rbenv/ruby-build v20200518

ruby-build 20200518

on GitHub

rbenv-install: show the short list by default

As suggested by @eregon, now we have "-l/--list" option for the short
list of versions. Behaviour of ruby-build --definitions is kept as
before for compatibility.

rbenv-install:
-L/--list-all full list
-l/--list short list

ruby-build:
-d/--definitions full list
-l/--list short list

The short list now shows only latest stable versions
for each Ruby implementations like the following:

2.5.8
2.6.6
2.7.1
jruby-9.2.11.1
maglev-1.0.0
mruby-2.1.0
rbx-4.15
truffleruby-20.0.0

Update to OpenSSL 1.1.1f for Ruby 2.5+

mark ruby 2.5 to security maintenance

CVE-2020-1967, bump openssl to 1.1.1g

PR: #1419 should be applied also bin/rbenv-install

Add artichoke-dev to install the latest Artichoke nightly build

Allow to install the latest official Artichoke nightly build from https://github.com/artichoke/nightly/releases