Expose low-level opendir/readdir dir traversal.

* stream.c (UTF_DECL_OPENDIR): Macro defined, to enable
w_opendir declaration in utf8.h.
(w_opendir): Static function removed.

* sysif.c (UTF_DECL_OPENDIR): Macro defined.
(dir_s): Symbol defined unconditionally now, regardless of
HAVE_PWUID.
(dirent_s): New symbol.
(dirent_st): New static variable.
(struct dir): New struct type.
(opendir_free, opendir_mark opendir_wrap, readdir_wrap): New
static functions.
(opendir_ops): New static structure.
(sysif_init): Intern dirent symbol. Create dirent structure
type. Register opendir and readdir intrinsic functions.
Register variables dt-blk, dt-chr, dt-dir, dt-fifo, dt-lnk,
dt-reg, dt-sock and dt-unknown.

* utf8.c (UTF8_DECL_OPENDIR): Macro defined.
(w_opendir): Function moved here from stream.c, and turned
external.

* utf8.h (w_opendir): Declared, conditionally on
UTF8_DECL_OPENDIR being defined, so that most modules that
include utf8.h don't have to include <dirent.h>.

* txr.1: Documented.

diff --git a/sysif.c b/sysif.c

1 files changed, 3 insertions, 0 deletions

diff --git a/utf8.h b/utf8.h
index a8c48757..6d775451 100644
--- a/utf8.h
+++ b/utf8.h
@@ -56,3 +56,6 @@ FILE *w_freopen(const wchar_t *, const wchar_t *, FILE *);
 FILE *w_fdopen(int, const wchar_t *);
 int w_remove(const wchar_t *);
 int w_rename(const wchar_t *, const wchar_t *);
+#ifdef UTF8_DECL_OPENDIR
+DIR *w_opendir(const wchar_t *wname);
+#endif