io.c: chomp CR at the end of read buffer
* io.c (rb_io_getline_fast): chomp CR followed by LF but separated
by the read buffer boundary. [ruby-core:91707] [Bug #15642]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_6@67207 b2dd03c8-39d4-4d8f-98ff-823fe69b080e