* lib/linux/gnu.c (getppid): New function.
* include/linux/x86/syscall.h (SYS_getppid): New macro.
* include/linux/x86_64/syscall.h (SYS_getppid): New macro.
* lib/stub/getlogin.c: New file.
* lib/stub/setvbuf.c: New file.
* lib/stub/sigblock.c: New file.
* lib/libc+gnu.c: Include them.
* include/linux/x86/syscall.h (SYS_chdir): New macro.
* include/linux/x86_64/syscall.h (SYS_chdir): New macro.
* include/stdio.h (_IOFBF, _IOLBF, _IONBF): New macro.
* include/errno.h (ENOEXEC, ECHILD): New macro.
* include/sys/wait.h (WNOHANG): New macro.
* lib/linux/gnu.c (chdir): New function.
* include/ar.h: New file.
* include/dirent.h: New file. Import from glibc-2.2.5.
* include/dirstream.h: Likewise.
* lib/dirent/__getdirentries.c: Likewise.
* lib/dirent/closedir.c: Likewise.
* lib/dirent/readdir.c (readdir): Likewise.
* lib/libc+gnu.c: Include them.
* include/linux/x86/syscall.h (SYS_getdents): New macro.
* include/linux/x86_64/syscall.h (SYS_getdents): Likewise.
* lib/linux/gnu.c (getdents): New function.
* include/limits.h (NAME_MAX): New macro.
* include/fcntl.h (O_DIRECTORY): New macro.
* scaffold/tests/readdir.dir: New directory.
* scaffold/tests/99-readdir.c: New file, use it.
* build-aux/check-mescc.sh (tests): Run it.