Mk/bsd.ruby.mk: Switch from 'USE_RUBY=yes' to 'USES=ruby'
Switch from 'USE_RUBY=yes' to 'USES=ruby'.
Notable changes are.
- Mk/bsd.ruby.mk is move to Mk/Uses/ruby.mk.
- 'USE_RUBY=yes' is replaced with 'USES=ruby'.
- 'USE_RUBY_EXTCONF' is replaced with 'USES=ruby:extconf'.
- 'USE_RUBY_RDOC' is replaced with 'USES=ruby:rdoc'.
- 'USE_RUBY_SETUP' is replaces with 'USES=ruby:setup'.
- 'RUBY_NO_BUILD_DEPENDS' and 'RUBY_NO_RUN_DEPENDS' are replaced with 'USES=ruby:{build,none,run}'.
- 'RUBY_REQUIRE' isn't used anywhere, so removed.
- 'USES=gem' now implies 'USES=ruby'.