Repeating the default WARNS here makes it slightly more difficult to
experiment with default WARNS changes, e.g. if we did something absolutely
bananas and introduced a WARNS=7 and wanted to try lifting the default to
that.
Drop most of them; there is one in the blake2 kernel module, but I suspect
it should be dropped -- the default WARNS in the rest of the build doesn't
currently apply to kernel modules, and I haven't put too much thought into
whether it makes sense to make it so.
Areas not covered still [positive functionality wise] are:
- sbuf_{clear,get,set}_flags
- sbuf_new (in particular, with fixed buffers, etc).
Some basic negative testing has been added, but more will be added in the
future.
This work was in part to validate work done by cem in r288223, and ian
before that.
MFC after: 2 months
Sponsored by: Dell EMC Isilon
