loci: only mask partially wildcarded fields

The of_match_values_mask function was consuming about 7% CPU time in my
benchmarks. For realistic flows most of the work it did was pointless, because
most fields are fully wildcarded and most of the rest are not wildcarded. Only
in the uncommon case of partially wildcarded fields does this function do
anything.

Fixed by calling a new of_memmask function only when parsing a masked OXM.
openflow_input: add bsn_pktin_flag extension
update VlanVid.ofVlan to accept NO_MASK
address review comment
Merge into master from pull request #248:
update VlanVid.ofVlan to accept NO_MASK (https://github.com/floodlight/loxigen/pull/248)
Merge into master from pull request #246:
Fix bsn_vport subtype and add l2gre vport (https://github.com/floodlight/loxigen/pull/246)
openflow_input: fix wire_type in ofp_bsn_pktin_flag
Merge into master from pull request #247:
openflow_input: add bsn_pktin_flag extension (https://github.com/floodlight/loxigen/pull/247)
loci: use of_memmask for OF 1.1
loci: cleanup of_memmask and remove of_match_values_mask
Merge into master from pull request #239:
loci: only mask partially wildcarded fields (https://github.com/floodlight/loxigen/pull/239)
loci: do not generate header classes for messages

These conflict with the real classes of the same name.
loci: link locitest with --whole-archive

This would have caught the duplicate symbols.
Merge into master from pull request #250:
loci: do not generate header classes for messages (https://github.com/floodlight/loxigen/pull/250)
Merge remote-tracking branch 'upstream/master'