Switched from old hashing functions to use Bob Jenkins' hash routine

- If the underlying type is contiguous, FixedList hashes its storage directly.
- Drop labelPairHash (non-commutative) from fvMeshDistribute since
  FixedList::Hash does the right thing anyhow.
- Hash<edge> specialization is commutative, without multiplication.
- Hash<triFace> specialization kept multiplication (but now uLabel).
  There's not much point optimizing it, since it's not used much anyhow.

Misc. changes

- added StaticAssert to NamedEnum.H
- label.H / uLabel.H : define FOAM_LABEL_MAX, FOAM_ULABEL_MAX with the
  values finally used for the storage.  These can be useful for pre-processor
  checks elsewhere (although I stopped needing them in the meantime).

applications/test/FixedList/FixedListTest.C

@@ -56,6 +56,12 @@ int main(int argc, char *argv[])
     Info<< "list:" << list
         << " hash:" << FixedList<label, 4>::Hash<>()(list) << endl;
 
+    Info<< "FixedList<label, ..> is contiguous, "
+        "thus hashing function is irrelevant: with string::hash" << endl;
+
+    Info<< "list:" << list
+        << " hash:" << FixedList<label, 4>::Hash<string::hash>()(list) << endl;
+
     label a[4] = {0, 1, 2, 3};
     FixedList<label, 4> list2(a);