Also, as it's in the middle of the list of 4 arguments, 3rd and 4th arguments
(trim_mode, eoutvar) are changed to keyword arguments.
Old ways to specify arguments are deprecated and warned now.

bin/erb: deprecate -S option.

We'll remove all of deprecated ones at Ruby 2.7+.

enc/make_encmake.rb: stopped using deprecated interface
ext/etc/mkconstants.rb: ditto
ext/socket/mkconstants.rb: ditto
sample/ripper/ruby2html.rb: ditto
spec/ruby/library/erb/defmethod/def_erb_method_spec.rb: ditto
spec/ruby/library/erb/new_spec.rb: ditto
test/erb/test_erb.rb: ditto
test/erb/test_erb_command.rb: ditto
tool/generic_erb.rb: ditto
tool/ruby_vm/helpers/dumper.rb: ditto
tool/transcode-tblgen.rb: ditto
lib/rdoc/erbio.rb: ditto
lib/rdoc/generator/darkfish.rb: ditto

[Feature #14256]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62529 b2dd03c8-39d4-4d8f-98ff-823fe69b080e