Fix value of OFPG_MAX

This constant was introduced with the value 0xffffff00 in version 1.3.1
of the spec.  Fix our macro to use the correct value.

Motivated by FlowForwarding/LINC-Switch#191.
Fix typo in type name ofp_group_mod_failed
Merge pull request #50 from legoscia/fix-OFPG_MAX

Fix value of OFPG_MAX
Merge pull request #56 from yamt/fix-table-feature-req

fix some of ofp_v4 table_feature_prop_type constants
Add unit tests for ofp_parser

We should also test parsing fragments smaller than 8 bytes: see
FlowForwarding/of_protocol#40.
Merge branch 'fix-parser' of github.com:yamt/of_protocol into yamt-fix-parser
Add unit test for parsing 7 byte fragments

This now works!
uncut_bits: comment
fix crashes with non openflow_basic match fields
change oxm on-wire length for ipv6_flabel and mpls_label

this is doubtful per spec but matches with ONF openflow.h and
other implementations.  (ovs, ryu, ...)