ndctl: release v54

This release incorporates the capabilities of the 4.8 kernel.  Updates
to the unit tests make up the bulk of this release to account for kernel
commit 1ee6667cd8d1 "libnvdimm, pfn, dax: fix initialization vs
autodetect for mode + alignment".

Commands:
    list: add device-dax information
    list: add btt size information
    create-namespace: fix handling of invalid sector sizes
    create-namespace: static analysis fixes
    bash-completion: namespace completion enhancements

Tests:
    libndctl: updates for pfn and dax autodetect changes
    libndctl: new gates for running against older kernels
    device-dax: new
    pcommit: remove, the pcommit instruction has been deprecated

Apis:
    ndctl_dimm_get_manufacturing_date: new
    ndctl_dimm_get_manufacturing_location: new
    ndctl_btt_get_size: new
    ndctl_cmd_unref: fix, accepts NULL input