updated to 7.4.492

updated to 7.4.492

7.4.482  when 'balloonexpr' results in a list, text has a trailing NL
7.4.483  a 0x80 byte is not handled correctly in abbreviations
7.4.484  (after 7.4.483) compiler warning
7.4.485  (after 7.4.484) abbreviations don't work
7.4.486  check for writing to a yank register is wrong
7.4.487  ":sign jump" may unnecessarily use another window
7.4.488  test_mapping fails for some people
7.4.489  cursor movement wrong when 'lbr' with a number column
7.4.490  cannot specify the buffer to use for "do" and "dp"
7.4.491  negative "topline" value for winrestview() has display errors
7.4.492  Ctrl-O in Insert mode moves right after insert comment leader