Markdown reader: Prevent spurious line breaks after list items.

When the `hard_line_breaks` option was specified, pandoc would
produce a spurious line break after a tight list item.  This
patch solves the problem.  Closes #1137.

src/Text/Pandoc/Readers/Markdown.hs

@@ -1560,7 +1560,8 @@ endline = try $ do
  guardEnabled Ext_blank_before_header <|> notFollowedBy (char '#') -- atx header
  guardDisabled Ext_backtick_code_blocks <|>
  notFollowedBy (() <$ (lookAhead (char '`') >> codeBlockFenced))
- (guardEnabled Ext_hard_line_breaks >> return (return B.linebreak))
+ (eof >> return mempty)
+ <|> (guardEnabled Ext_hard_line_breaks >> return (return B.linebreak))
  <|> (guardEnabled Ext_ignore_line_breaks >> return mempty)
  <|> (return $ return B.space)