net_device: Optimized for 1GB huge pages.

translate_physical_addr() and map_from_guest() switched from the
software TLB to a simple one-element cache of the most recent
referenced page. (With 1GB pages there is normally only one page so
the cache should always hit.)

map_to_guest() removed because it was not used.
memory.virtual_to_physical(): drop use of TLB cache.
bench_env/include_checks.sh: Don't check hugepages.

This test is not appropriate with 1GB HugeTLBs.
Merge pull request #211 from lukego/hugetlb1G

1G HugeTLB optimizations