Bug#107826: can not create file through a dangling symlink

[Roland McGrath]

This behavior is implemented explicitly in libdiskfs/dir-lookup.c line 374:

           /* Symlinks to nonexistent files aren't allowed to cause
               creation, so clear the flag here. */
           create = 0;

Try removing that line and see if everything works right.

I just checked the austin group draft 7 spec and though I didn't find
anything explicitly about this case off hand, it seems to specify the
creation behavior.  That is how Linux and FreeBSD both behave, so we should
match.

In skimming a couple parts of the spec, I also noticed it now explicitly
says that a lookup of "" must fail.  So we should change this too.

These things differed in traditional Unix behavior, and in BSD until fairly
recently, but the new specs on the horizon require everyone to match the
System V style behavior.