* ext/readline/extconf.rb, ext/readline/readline.c: check
  RL_PROMPT_START_IGNORE and RL_PROMPT_END_IGNORE directly in
  readline.c.  Patch by Zachary Scott.  [Bug #7397] [ruby-core:49561]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39002 b2dd03c8-39d4-4d8f-98ff-823fe69b080e