For glibc, implementing realloc (p, s) as realloc (p, s?s:1) suffices,
and it’s probably better to do it inline to aid static checking.
* lib/realloc.c (rpl_realloc) [_GL_INLINE_RPL_REALLOC]:
Remove, replacing with inline function in stdlib.h.
* lib/stdlib.in.h (_GL_INLINE_RPL_REALLOC): New macro.
(rpl_realloc): Define as inline if _GL_INLINE_RPL_REALLOC.
* m4/realloc.m4 (gl_FUNC_REALLOC_0_NONNULL):
Set REPLACE_REALLOC_FOR_REALLOC_POSIX=2 instead of 1,
if it’s close enough to glibc that the inline optimization is valid.