LU-1606 api: Rename liblustreapi.h -> lustreapi.h

LU-1606 api: Rename liblustreapi.h -> lustreapi.h

The header file "liblustreapi.h" is unfortunately named,
implying that it is only part of the lustre-in-user-space-client
rather than the more general lustre api for users that it is.

This patch renames it to simply "lustreapi.h" to avoid that
confusion.  This also helps to move towards making it
easier to use the lustre API for users.  They can simply

  #include <lustre/lustreapi.h>

and then compile with "-llustreapi".

For backwards compatibility, liblustreapi.h becomes a stub
that includes lustreapi.h, and can be removed at some date
in the future.

Since LU-113, LASSERT should be removed from userspace.
In this change, lustre_user.h has had LASSERTs removed.

All code examples in the man pages have been tested.

Signed-off-by: Christopher J. Morrone <morrone2@llnl.gov>
Signed-off-by: Richard Henwood <richard.henwood@intel.com>
Change-Id: Id1e709d36a855ad2a8eff206fa9f6bbe87182a29
Reviewed-on: http://review.whamcloud.com/3427
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>