demmt: decode IB entries

Initial support.
demmt: add option to dump ioctl data
demmt: track gpu addresses

note: needs latest valgrind-mmt fixes
demmt: add option to print gpu addresses for reads and writes
demmt: parse IB entries

With a help of -n option.
Revert "demmt: hacky IB trick detection"

It's not needed anymore. Adding IB support was easier than I expected.