ruby: update to 2.2.0

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>

lang/ruby/patches/001-rdoc-remove_gems_dep.patch

@@ -1,3 +1,7 @@
+References:
+
+https://github.com/rdoc/rdoc/pull/340
+
 --- ruby-2.1.2.orig/lib/rdoc.rb	2014-09-02 17:14:28.719224215 -0300
 +++ ruby-2.1.2/lib/rdoc.rb	2014-09-02 17:14:28.762223911 -0300
 @@ -109,6 +109,8 @@