LoxiGen: start generating pyloxi 1.3

Not all classes are fully implemented.
pyloxi: generate OXM classes
pyloxi: implement of_ipv6_t
LoxiGen: add OF 1.3 OF_HELLO_ELEM_TYPE group
pyloxi: support hello_elems
frontend: factor out code to add a single identifier

No functional change.
frontend: parse enums from input files
use identifiers parsed from input files
openflow_input: add ofp_nicira_controller_role enum
convert enum values to integers

Previously the enum values given to the backends were strings of C code.
Luckily the code was simple enough that it was also valid Python. Moving the
conversion to the frontend makes it easier to move enum definitions into the
input files, and cleans up some pyloxi code.
openflow_input: add all enums
remove canonical header file parsing

This has been completely replaced with the openflow_input files.
Merge branch 'parse-enums'
Merge branch 'master' into pyloxi-1.3

Also added ofp_hello_elem_type to standard-1.3.

Conflicts:
	loxi_front_end/translation.py
Merge pull request #2 from rlane/pyloxi-1.3

Initial PyLoxi 1.3 work
Fix code generation on 32 bit operational systems.
Python types are different on 32 and 64 bit systems for equal values.
e.g: The value 0xffffffff is considered long on 32 bit systems and
int on 64 bit systems.
Merge pull request #6 from ederlf/master

Fix code generation on 32 bit systems.
pyloxi: add basic test cases for of11 and of12

Also fixes minor bugs when importing those modules, and adds a check-py target
to run all the unit tests against the generated code.
pyloxi: add loxi.version_names
pyloxi: include all members in OFClass.members

This preserves ordering, which is important because we can't rely on the offset
field for sorting (it may be -1).

The newly passing show() tests are due to the side effect of removing type
fields from pretty printing.