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).

src/OpenFOAM/primitives/strings/string/string.H

@@ -47,6 +47,7 @@ SourceFiles
 #define string_H
 
 #include "char.H"
+#include "Hasher.H"
 
 #include <string>
 #include <cstring>
@@ -92,7 +93,7 @@ public:
         hash()
         {}
 
-        inline unsigned operator()(const string&) const;
+        inline unsigned operator()(const string&, unsigned seed = 0) const;
     };