Try to use huge pages to store ringbuffers

[lw]

Latency-sensitive applications, like the transports, that use ringbuffers as intermediate storage for the data (think SHM, or InfiniBand), might benefit from using huge pages to avoid hitting as many page faults and interrupts. Huge pages are however a bit finicky: we thought we were supporting them but it turned out we were passing the flags incorrectly; and doing that the right way raises an error if huge pages are disabled/unavailable. Having been unable to get huge pages to work, I don't know how much performance benefit they can bring and whether they're worth investing in some graceful fallback logic.