[SR-933] 'flatten()' should be renamed to 'flattened()'

[natecook1000]

Previous ID	SR-933
Radar	None
Original Reporter	@natecook1000
Type	Bug
Status	Resolved
Resolution	Won't Do

Additional Detail from JIRA

Votes	1
Component/s	Standard Library
Labels	Bug
Assignee	arsen (JIRA)
Priority	Medium

md5: da39cc6caa626ce0181caeeae8a39fe8

Issue Description:

The 'flatten()' method didn't get the Swift 3 API renaming treatment it should have, to go along with reversed, sorted, joined, etc.

[ole]

Resolved by SE-0133: Rename flatten() to joined().

Implemented by:

• [stdlib] Rename flatten() to joined() (SE-0133) #3809

• [stdlib] default separator for joining strings (SE-0133) #3838

• [stdlib] Update doc comments for SE-0133 #3839