* mkdir-p.c (ENOSYS): Define to EEXIST if not defined.

* mkdir-p.c (ENOSYS): Define to EEXIST if not defined.
(make_dir_parents): Treat ENOSYS like EEXIST.

Improve quality of diagnostics on restore_cwd failure.
* mkdir-p.h (make_dir): Remove.  All uses replaced by mkdir.
(make_dir_parents): Last arg is now int * (for errno), not bool *.
* mkdir-p.c (make_dir, make_dir_parents): Likewise.
Rewrite "mkdir -p" algorithm to avoid the need for "stat"
each time through the loop.  Do not diagnose restore_cwd failure;
that is the caller's job (and perhaps the caller does not care).

* mkdir-p.c (CLEANUP_CWD, CLEANUP): Remove.
(make_dir_parents): Revamp to avoid need for CLEANUP_CWD, CLEANUP.
If the file already exists but is not a directory, don't bother
to try to make its parents.
Close potential file descriptor leak if we can't chdir("/") (!).
Don't always return true if chdir($PWD) fails; return true only
if the requested action was done successfully (except for the
chdir($PWD)).
Don't log final directory unless we actually made it.
Refactor to avoid duplicate code to fix up permissions.
Don't attempt to fix up parent permissions if chdir($PWD) fails.

* mkdir-p.c (make_dir_parents): Don't let a failed chdir($PWD)
stop us from restricting permissions of just-created absolute-named
directories.
* mkdir-p.c (CLEANUP_CWD): Return *true*, not false when failing
to restore initial working directory.
* mkdir-p.c (make_dir_parents): New parameter: different_working_dir,
to tell caller if/when we change the working directory and are
unable to return to the initial one.
* mkdir-p.h (make_dir_parents): Update prototype.
* mkdir-p.c (CLEANUP_CWD): Change one more `return 1' to
`return false'.  This fixes a bug introduced on 2004-07-30.
Assume HAVE_UNISTD_H, i.e., include <unistd.h> unconditionally.
Assume HAVE_FCNTL_H (i.e., include <fcntl.h> unconditionally,
and don't include <sys/file.h>).