Begin breaking openflow-1.0.h into common and version-specific definitions.

Begin breaking openflow-1.0.h into common and version-specific definitions.

The intention is that, as each OpenFlow 1.1 and 1.2 feature is added to Open
vSwitch, the corresponding protocol definitions will be broken up this way:

  - Definitions that are the same in OF1.0 and OF1.1 will retain the "OFP"
    or "ofp" prefix and move to openflow-common.h.

  - Definitions that are specific to OF1.0 will be renamed with an "OFP10"
    or "ofp10" prefix and stay in openflow-1.0.h.

  - Definitions that are specific to OF1.1 or to OF1.1 and OF1.2 will be
    renamed with an "OFP11" or "ofp11" prefix and move to openflow-1.1.h.

  - Definitions that are specific to OF1.2 will be renamed with an "OFP12"
    or "ofp12" prefix and move to openflow-1.2.h.

This commit starts this process with some basic OpenFlow definitions.

Reviewed-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ben Pfaff <blp@nicira.com>