ruby: bump to 2.5.0

ruby: bump to 2.5.0

2.5.0 introduces many new features and performance improvements.
See: https://www.ruby-lang.org/en/news/2017/12/25/ruby-2-5-0-released/

Packaging changes:
* As date was promoted into a gem, ruby-datetime
  was splitted into ruby-date and ruby-time
* New packages for gemified stdlib files:
  - ruby-cmath (from ruby-math)
  - ruby-date (from ruby-datetime)
  - ruby-etc (from ruby-misc)
  - ruby-fcntl (from ruby-misc)
  - ruby-fileutils (from ruby-filelib)
  - ruby-ipaddr (from ruby-socket)
  - ruby-scanf (from ruby-misc)
  - ruby-stringio (from ruby-misc)
  - ruby-strscan (from ruby-misc)

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>