Add JRuby 9.1.15.0

Relax java version regexp

num_cpu_cores: Prefer getconf over cpuinfo grep, simplify grep usage

Add definition for JRuby 9.1.14.0

## Summary

JRuby 9.1.14.0 has been released.
http://jruby.org/2017/11/08/jruby-9-1-14-0.html

## Other Information

JRuby 9.1.14.0+ download URL has changed.
https://github.com/rbenv/ruby-build/issues/1148

Fix OpenSSL version

Upgrade to OpenSSL 1.0.2m and 1.1.0g

Added 2.5.0-preview1 definition

This allows the java version to be specified as "9", instead of "1.9".

Closes #1135

Add rbx-3.83 and rbx-3.84

`--quiet` option isn't sensible sha256sum(1) of GNU coreutils

The option is available only if verifying digest, not available when computing digest.

>       --quiet
>              don't print OK for each successfully verified file

Quote JRuby check on FreeBSD to avoid "unary operator" syntax issue.

Ignore everything after whitespace in the output from sha256sum

Add JRuby 9.1.13.0

The issue has originarily reported as pyenv/pyenv#902.

Unlike sha256sum of GNU coreutils, BusyBox one doesn't print '*'
and prints extra whitespaces, when computing digest from stdin.

sha256sum (GNU coreutils 8.26)

```
% cat /sbin/init | sha256sum -b
ef753e9504ada221155b86e7e6b7b4ff2499d64e27bcd959f0542bcac589feb1 *-
```

sha256sum (BusyBox v1.26.2)

```
/ # cat /sbin/init | sha256sum -b
4cd6d1a4028772fabc9166bb52b5826aec4e91874c107fce33dc515c04cb754f  -
```

I also confirmed that md5sum behaves just similarly.

Add mruby 1.3.0

Release:
https://github.com/mruby/mruby/releases/tag/1.3.0

Announcementns:
http://mruby.org/releases/2017/07/04/mruby-1.3.0-released.html

Closes #1106

Add JRuby 9.2.0.0 snapshot

Improve check for openssl on macOS

Add rbx-3.81 and rbx-3.82