Merge branch 'fix-8.3'
Merge branch 'release-9'
Merge branch 'fix-9.1'
Merge branch 'fix-9.1'
Drop all start attributes.
Remove end attributes.
Copy layout files to v17.
Replace left right attributes with their start and end variants.
Remove invalid v17+ attributes from base layouts.
Push version to 191 and v9.2.
Set platform appropriate gravity.
Create some v17 styles using new start and end attributes.
Merge branch 'fix-9.2' into beta