Enforce element types of DASH containers to be trivially copyable

[devreal]

Consistently enforce std::is_trivially_copyable on element types of containers (except when using the Cray compiler).
Introduce minimum required compiler version.
Makes GlobPtr trivially copyable after #221 has been resolved.
Introduce dash::Pair which closely resembles std::pair except for being trivially copyable.
Fixes #241

[fuchsto]

Intel compilers (tested 16.0 and 17.0) don't allow std::is_trivially_copyable either. Why did you remove this check?

[devreal]

Because they do. I just tested with Intel 17.0 and I am sure I also verified 16 back when we discussed #241. Keep in mind that the Intel compiler relies on the GNU-provided STL so you might have to load a newer GCC module (at least I have to do that on our Linux cluster).

[fuchsto]

Yes, that seems alright.
I actually did test exactly that, but it's apparently specific to our dev server. When reloading gcc after loading the icc module, there is some hickup and the newer version of gcc is not used.

[devreal]

@fuchsto Just checked with Clang 3.8.0, works fine for me. What version did you test with?

How would you check trivial-copyable in a custom type trait? std::is_trivially_copyable relies on the compiler builtin function __is_trivially_copyable...

[fuchsto]

@devreal We could define traits depending on the compiler and its version. If this is just an issue with Cray compilers, it's not worth the effort, of course.