gridCompare: don't check nvertex and number of unstructured grids with same uuid and missing coordinates

* This reverts r3646 and r3645.
* xrealloc/xmalloc are there for a reason:
** Every call to these functions does not check the return value of
   the memory allocation, hence error checking must be performed
   in the wrapper.
** This was historically done in the macros defined in dmemory.h,
   but redefining any identifier from the standard library to
   something which behaves differently is confusing.

* Also rename some functions to include cdi prefix.

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

* Also compare uuid in grid comparison.

* RFC 4122 does not guarantee octet 0 to be non-zero.

* reshGetVal never returns NULL.

* This way CDI can still be built with pgcc 11.x.

* Also extend Fortran 2003 interface generator accordingly.