add enable_if as an stl-conforming replacement of EnableIf.  Take it from the library header if present.  Deprecate EnableIf

[[Imported from SVN: r5396]]

[[Imported from SVN: r5321]]

the classes RemoveConst and SameType, which have been deprecated in 1.1, are now removed.  Use remove_const and is_same instead

[[Imported from SVN: r5133]]

[[Imported from SVN: r5032]]

[[Imported from SVN: r5031]]

[[Imported from SVN: r5005]]

[[Imported from SVN: r4963]]

Put the classes SameType and RemoveConst back in for backward compatibility.  Marking them as deprecated doesn't work, due to gcc bug 16370

[[Imported from SVN: r4888]]

[[Imported from SVN: r4857]]

[[Imported from SVN: r4848]]

[[Imported from SVN: r4847]]

RemoveConst (except that the return type is now 'type' instead of 'Type').
If the tr1/type_traits header is present, remove_const will be taken from
there.  If not, remove_const is a copy of the RemoveConst class in this
file.

[[Imported from SVN: r4844]]

[[Imported from SVN: r4784]]

[[Imported from SVN: r4734]]

[[Imported from SVN: r4679]]

[[Imported from SVN: r4012]]

[[Imported from SVN: r3348]]

[[Imported from SVN: r3086]]

[[Imported from SVN: r2958]]

EnableIfInterOperable::type to EnableIfInterOperable::Type as this is
more consistent with the Dune Programming guidelines.

Please change your code accordingly. The type with small t will be
removed eventually.

[[Imported from SVN: r1856]]

[[Imported from SVN: r1716]]

[[Imported from SVN: r1715]]

[[Imported from SVN: r1499]]

[[Imported from SVN: r1321]]

[[Imported from SVN: r1304]]

variables by anonymous enums.

[[Imported from SVN: r1225]]

[[Imported from SVN: r1029]]