* malloc et al. can return NULL on zero-size allocations.
* this commit also reverts the dubious calling of calloc by xmalloc.

* reshGetVal(ue) will always return non-NULL pointers.

* Eliminate unused fields.

* See r2661.

* This change creates an archive containing resource_unpack.c only for
  use in test programs.

* This test currently only checks if a single missing value is
  successfully written out and counted on input.