For ruby changes since 2.1.x:

 https://github.com/ruby/ruby/blob/v2_2_0/NEWS

Relevant changes for OpenWRT:

* all patches for ruby-core where merged upstream and
  they are not needed anymore (only rdoc patch remains)
 - PR for the rdoc github project was added to the patch header
   (https://github.com/rdoc/rdoc/pull/340)
* new package ruby-powerassert for introduced new bundled gem power_assert
* new package ruby-unicodenormalize for Unicode normalization files
* removed ruby-dl as DL was removed after being deprecated
* ruby-{minitest,testunit} where removed from ruby library. Now they
  are bundled gems
* test and sample files where removed from gems in order to save resources
  and reduce pkgs dependencies
* script ruby_find_pkgsdeps was updated to match upstream changes

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

rdoc seems to be written to run without gem. However,
some internal code still does not check for gems presence.
With a small patch, rdoc can run without gems.

Ref: https://bugs.ruby-lang.org/issues/10196

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