* Instead of vars in order dictated by client streamWriteVar.
* This allows for differential handling of different stream types.

* This way all header elements can later be accessed directly.

* This will later ease distinguishing both in the MPI window index.

* Also eliminate unused variables.

* Eliminate unneeded variable through varargs capability of xabort.
* Fix incorrect output format directives for size_t parameters.
* Fix incorrect output format directive for long parameters.

* It's already in atexit.