fix for #9336 changed the signature of getextmntent()

[tsoome]

The change d31277a did change

int getextmntent(FILE *, struct extmnttab *, size_t);

to

int getextmntent(const char *path, struct extmnttab *entry, struct stat64 *statbuf);

which is not really good idea, because getextmntent() is part of libc in Solaris from version Solaris 8 and is included in current version of illumos as well.

It would better to rename it.

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[lundman]

I just had to rewrite the code for Windows for this function, as it wasn't thread safe, and we do concurrent mounts on import. I'm especially not happy with threadsafe static struct mntent .... to hold the data (Windows and FreeBSD do this at least).

So I am happy to fix it, as for how we fix it, rename is ok by me.