Remove vestigial 3DFS support code (re: f88f302c)

Support for the long-dead 3DFS userland versioning file system was
already removed from ksh93 (although I'd overlooked some minor
things), but libast still supported it. This removes that too.

src/lib/libast/include/fs3d.h,
src/lib/libast/man/fs3d.3,
src/lib/libast/misc/fs3d.c:
- Removed.

bin/package,
src/cmd/INIT/package.sh:
- Remove attempted use of removed vpath builtin.

src/cmd/ksh93/*:
- Remove minor 3dfs vestiges.

src/lib/lib{ast,cmd,coshell}/*:
- Remove code supporting 3dfs.

src/lib/libast/dir/dirlib.h

@@ -132,17 +132,11 @@ __STDPP__directive pragma pp:nohide DIR closedir opendir readdir seekdir telldir
 	int		dd_size;	/* valid data in block		*/ \
 	char*		dd_buf;		/* directory block		*/
 
-#ifdef _BLD_3d
-#define DIR		DIRDIR
-#endif
 #undef	_DIRENT_H
 #include "dirstd.h"
 #ifndef _DIRENT_H
 #define _DIRENT_H	1
 #endif
-#ifdef _BLD_3d
-#undef	DIR
-#endif
 
 #ifndef	DIRBLKSIZ
 #ifdef	DIRBLK

src/lib/libast/dir/dirstd.h

@@ -45,8 +45,6 @@ struct dirent
 	char		d_name[1];	/* entry name			*/
 };
 
-#ifndef _BLD_3d
-
 #ifdef	rewinddir
 #undef	rewinddir
 #define rewinddir(p)	seekdir(p,0L)
@@ -59,5 +57,3 @@ extern void		seekdir(DIR*, long);
 extern long		telldir(DIR*);
 
 #endif
-
-#endif