[oe] Updating libtiff

[Tom Rini]

Hey all,

I'm looking to update libtiff to cover some security issues in the 
version we ship, and I noticed something funny about how we do it today. 
  Currently tiff_3.9.2.bb sets PV to 3.9.2+4.0.0beta5 and grabs and 
builds 4.0.0beta5.  While it's possible that in the past 3.9.2 was 
intended to be the last 3.9.x, it wasn't.

I think we should go with:
- Add tiff_4.0.0beta6.bb which should be compatible with beta5 and will 
get upgrades right.
- Add tiff_3.9.4.bb as well, in case someone wants to stay on the 
released line.

Anyone see a problem with that?

-- 
Tom Rini
Mentor Graphics Corporation