Created attachment 370565 [details] [review]
Reverse arguments to et_file_tag_copy_other_into, destination is first.

I've found this issue with Fedora 27, 2.4.3-4.
To reproduce:
1. extract a single track of a well-known CD in rhythmbox as FLAC
2. rhythmbox typically populates the following tags:
	album
	artist
	artistsort
	date
	discid
	discnumber
	genre
	musicbrainz_albumartistid
	musicbrainz_albumid
	musicbrainz_artistid
	musicbrainz_discid
	musicbrainz_trackid
	title
	tracknumber
	tracktotal
3. Open the track with easytag
4. Easytag will complain that the date is wrong (2018-01-01 while it wants 2018) and will mark the file as modified.
5. Save
6. The tag list is now:
	album
	artist
	date
	discnumber
	genre
	title
	tracknumber
	tracktotal

All the unknown tags (musicbrainz-*, artistsort, discid) have been lost.

I've tracked it to swapped arguments with calling et_file_tag_copy_other_into(), the source and destination have been swapped.
With the attached patch, easytag functions correctly.