* lib/linux/_getcwd.c: Rename from getcwd.c.
* lib/linux/_open3.c: Rename from open.c.
* lib/posix/getcwd.c: New file with bits from ../linux/getcwd.c.
* lib/posix/open.c: New file with bits ../linux/getcwd.c.
* build-aux/build-lib.sh (libc_SOURCES): Update.
* lib/linux/access.c: New file.
* lib/linux/brk.c: New file.
* lib/linux/chmod.c: New file.
* lib/linux/dup.c: New file.
* lib/linux/dup2.c: New file.
* lib/linux/execve.c: New file.
* lib/linux/fork.c: New file.
* lib/linux/fsync.c: New file.
* lib/linux/getcwd.c: New file.
* lib/linux/ioctl.c: New file.
* lib/linux/libc.c: New file.
* lib/linux/open.c: New file.
* lib/linux/read.c: New file.
* lib/linux/unlink.c: New file.
* lib/linux/waitpid.c: New file.
* lib/linux/libc.c: Include them.
(access, brk, chmod, dup, dup2, execve, fork, fsync, getcwd, ioctl,
libc, open, read, unlink, waitpid): Remove.