Places a comment above key from group_name.
If key is null then comment will be written above
group_name. If both key and group_name are null, then
comment will be written above the first group in the file.
| this |
a KeyFile |
| group_name |
a group name, or null |
| key |
a key |
| comment |
a comment |
|
true if the comment was written, false otherwise |