[DRE-maint] Bug#784210: ruby-setup: update required module name to RbConfig

[Ralph Amissah]

Source: ruby-setup
Severity: important
Tags: upstream

Dear Maintainer,
Browsing current source it seems line 789 should now be RbConfig::CONFIG (rather than Config::CONFIG) else if working now, there are likely to be problems with subsequent versions of Ruby.

s/::Config::CONFIG/::RbConfig::CONFIG

Similar issues may exist with other ruby libs?

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (500, 'stable'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 3.16.0-4-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to en_US.UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)