Prototype/structure update for Linux

Prototype/structure update for Linux

I appologize in advance why to many things ended up in this commit.
When it could be seperated in to a whole series of commits teasing
that all apart now would take considerable time and I'm not sure
there's much merrit in it.  As such I'll just summerize the intent
of the changes which are all (or partly) in this commit.  Broadly
the intent is to remove as much Solaris specific code as possible
and replace it with native Linux equivilants.  More specifically:

1) Replace all instances of zfsvfs_t with zfs_sb_t.  While the
type is largely the same calling it private super block data
rather than a zfsvfs is more consistent with how Linux names
this.  While non critical it makes the code easier to read when
your thinking in Linux friendly VFS terms.

2) Replace vnode_t with struct inode.  The Linux VFS doesn't have
the notion of a vnode and there's absolutely no good reason to
create one.  There are in fact several good reasons to remove it.
It just adds overhead on Linux if we were to manage one, it
conplicates the code, and it likely will lead to bugs so there's
a good change it will be out of date.  The code has been updated
to remove all need for this type.

3) Replace all vtype_t's with umode types.  Along with this shift
all uses of types to mode bits.  The Solaris code would pass a
vtype which is redundant with the Linux mode.  Just update all the
code to use the Linux mode macros and remove this redundancy.

4) Remove using of vn_* helpers and replace where needed with
inode helpers.  The big example here is creating iput_aync to
replace vn_rele_async.  Other vn helpers will be addressed as
needed but they should be be emulated.  They are a Solaris VFS'ism
and should simply be replaced with Linux equivilants.

5) Update znode alloc/free code.  Under Linux it's common to
embed the inode specific data with the inode itself.  This removes
the need for an extra memory allocation.  In zfs this information
is called a znode and it now embeds the inode with it.  Allocators
have been updated accordingly.

6) Minimal integration with the vfs flags for setting up the
super block and handling mount options has been added this
code will need to be refined but functionally it's all there.

This will be the first and last of these to large to review commits.