datapath: Add support for Linux 3.11

Kernel 3.11 has support for extended GRE API required for
OVS datapath,  But vxlan still needs out of tree tunneling
compatibility.  Therefore to simplify, all tunneling modules
are forced to use compat tunneling.

CC: James Page <james.page@ubuntu.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Jesse Gross <jesse@nicira.com>
FAQ: Add Q&A about bridge compatibility.

Signed-off-by: Ben Pfaff <blp@nicira.com>
FAQ: Fix misspelling.

Signed-off-by: Ben Pfaff <blp@nicira.com>
configure: check for uuid python module

After introducing commit a5ae88ff8a276e86c842ac102145432662bf711a
"ovsdb-doc: generate vswitch.[pic|gv] files only if dot tool is
available" Open vSwitch did not build anymore on hosts that did not
have uuid python module installed (for example, we still support
XenServer that still uses old python 2.4 and hence does not have uuid).

After this commit ./configure will check whether uuid module is present
and, if it isn't, then it will add python/compat to the PYTHONPATH.

Acked-By: Ben Pfaff <blp@nicira.com>
Signed-Off-By: Ansis Atteka <aatteka@nicira.com>
Issue: 20476
ovs-vtep: Don't flood to multiple 'uknown-dsts'.

This commit changes VTEP simulator's flooding logic as follows:

1. Traffic coming from a VTEP physical port will only be flooded
to all the physical ports in the same VTEP that belongs to that logical
switch and to ONLY one of the devices that have been marked as 'unknown-dst'

2. Traffic coming from any device that has 'unknown-dst' marked, will only be
flooded by VTEP to its physical ports that belong to that logical switch.

Bug #20144.
Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>
Acked-by: Justin Pettit <jpettit@nicira.com>