Prohibit views targeting AnyVal

Library changes in Scala 2.10 mean that we are left with the
unfortunate situation of admitting:

    scala> "": AnyVal
    res0: AnyVal =

 We already have explicit checks in place to prevent views
 targeting `AnyRef`. This commit balances this out by prohibiting
 `AnyVal`, as well.

The enclosed test shows that this case is now prevented. If multiple
implicits views are applicable, the ambiguity error is still raised;
these check comes right at the end. Maybe that ought to be changed,
but I don't think it matters too much.

I've also disabled this prohibition under -Xsource:2.10.
SI-8213 AnyRefMap.getOrElseUpdate is faulty

Altered getOrElseUpdate to be robust to the map changing out from under it as a result of calling the default value method.  Side-effects FTW!

Made a comparable change in LongMap also, as it was also affected.  And added a test to SetMapConsistencyTest.
Merge pull request #3416 from retronym/topic/any-val-implicit

Prohibit views targeting AnyVal
Merge pull request #3434 from Ichoran/issue/8213

SI-8213 AnyRefMap.getOrElseUpdate is faulty