Squashed 'sequence/' changes from efeb0fc..a5a1315

a5a1315 implement Set.Adapt.of_list for < 4.02
cdae072 removed many warnings
0226a4c more warnings enabled; fix tests
22705b2 change name of IO functions (keep compat)
REVERT: efeb0fc merge from master; version 0.5.4
REVERT: 2691bee version 0.5.3
REVERT: a373739 merge from master
REVERT: 0d721a6 release 0.5.2
REVERT: a50f307 merge from master
REVERT: e5625c6 merge from master: version 0.5.1
REVERT: 2ae771f oasis files

git-subtree-dir: sequence
git-subtree-split: a5a1315f7915761f2a85f3d0b7f88b81fb0a8f1d
Merge commit '2a0ebbeaf79608503428731f7531d18cb0822601' from sequence