* string.c (rb_str_enumerate_lines): make String#each_line and
  #lines not raise invalid byte sequence error when it is called
  with an argument. The patch also causes performance improvement.
  [ruby-dev:47549] [Bug #8698]

* test/ruby/test_m17n_comb.rb (test_str_each_line): remove
  assertions which check that String#each_line and #lines will
  raise an error if the receiver includes invalid byte sequence.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42966 b2dd03c8-39d4-4d8f-98ff-823fe69b080e