* lib/xalloc.h (XMALLOC, XNMALLOC, XZALLOC, XCALLOC): Move
definitions up, to avoid colliding with change below.
(static_inline) [HAVE_INLINE]: New macro.
(xnmalloc, xnrealloc, x2nrealloc, xcharalloc):
Provide extern decls when !HAVE_INLINE. Do not define unless
static_inline is defined, either by us or by xmalloc.c. Use
static_inline rather than static inline.
(XCALLOC): Optimize sizeof(T) = 1 case.
* lib/xmalloc.c (static_inline) [!HAVE_INLINE]: New macro.