getdelim: remove dependency on realloc-posix * lib/canonicalize-lgpl.c (alloc_failed) [!FUNC_REALPATH_WORKS || defined _LIBC]: New function, (__realpath) [!FUNC_REALPATH_WORKS || defined _LIBC]: Use it. Use __set_errno where needed, for consistency. * lib/getdelim.c (alloc_failed): New function. (getdelim): Use it. * modules/getdelim (Depends-on): Remove realloc-posix.