Move xpalloc from dfa.c to xmalloc.c and change it from static to
extern. The function is useful in other contexts; I’m about to
use it in coreutils.
* lib/dfa.c: Include idx.h, instead of rolling our own idx_t and
IDX_MAX. Do not include intprops.h; no longer needed.
(xpalloc): Move from here ...
* lib/xmalloc.c (xpalloc): ... to here, and make it extern.
Include intprops.h and minmax.h, needed by xpalloc.
* lib/xalloc.h: Include idx.h, for idx_t.
* modules/dfa (Depends-on): Add idx; remove intprops.
* modules/xalloc (Depends-on): Add idx, intprops, minmax.