SI-6632 ListBuffer's updated accepts negative positions

Changed the behavior in SeqLike.updated (which would silently accept negatives and throw on empty.tail) to throw IndexOutOfBoundException.

Updated tests to verify the behavior in ListBuffer.  Everything else SeqLike will come along for the ride.
SI-8177 specializeSym must use memberInfo on high side

When determining whether member `symLo` of `tpLo`
has a stronger type than member `symHi` of `tpHi`,
should we use memberType or memberInfo?

Well, memberType transforms (using `asSeenFrom`) `sym.tpe`,
whereas memberInfo performs the same transform on `sym.info`.
For term symbols, this ends up being the same thing (`sym.tpe == sym.info`).
For type symbols, however, the `.info` of an abstract type member
is defined by its bounds, whereas its `.tpe` is a `TypeRef` to that type symbol,
so that `sym.tpe <:< sym.info`, but not the other way around.

Thus, for the strongest (correct) result,
we should use `memberType` on the low side.

On the high side, we should use the result appropriate
for the right side of the `<:<` above (`memberInfo`).

I also optimized the method a little bit by avoiding calling memberType
if the symbol on the high side isn't eligble (e.g., it's a class).

PS: I had to add a workaround to reifyType, because
we now dealias a little less eagerly, which means
a type selection on refinement class symbols makes it to reify
this broke the t8104 tests.
I also had to update the run/t6992 test, which should now test the right thing.
Tests should be commented and/or use sensible names.
What is it testing? What is the expected outcome? We should not be left guessing.
SI-8188 NPE during deserialization of TrieMap

The writer was using the constructor headf and ef instead of the internal vars hashingobj and equalityobj.
SI-8177 tidy up in type reification
Merge pull request #3525 from adriaanm/t8177b

SI-8177 specializeSym must use memberInfo on high side
Merge pull request #3530 from Ichoran/issue/6632

SI-6632 ListBuffer's updated accepts negative positions
Merge pull request #3531 from Ichoran/issue/8188

SI-8188 NPE during deserialization of TrieMap