Part of rdar://175677817.

If the fix-it would remove a range that is followed by a newline and the
remaining text on the line is empty or all whitespace then remove the entire
line. This produces better results when a fix-it removes an attribute that is
written on a line by itself.

…inations.

Expand the fix-its to cover declarations with availability that is split
accross multiple attributes instead listed together in a single short form
`@available` attribute.

Resolves rdar://175677817.