ndctl: release v50

This release incorporates the capabilities of the 4.5 kernel, and adds
the below features and fixes:

New apis:
    ndctl_bus_get_ctx
    ndctl_namespace_get_pfn
    ndctl_namespace_get_mode
    ndctl_namespace_get_numa_node
    ndctl_region_get_pfn_seed
    ndctl_pfn_get_first
    ndctl_pfn_get_next
    ndctl_pfn_get_id
    ndctl_pfn_get_namespace
    ndctl_pfn_get_uuid
    ndctl_pfn_set_uuid
    ndctl_pfn_get_location
    ndctl_pfn_set_location
    ndctl_pfn_get_align
    ndctl_pfn_set_align
    ndctl_pfn_set_namespace
    ndctl_pfn_get_bus
    ndctl_pfn_get_ctx
    ndctl_pfn_get_devname
    ndctl_pfn_get_block_device
    ndctl_pfn_is_valid
    ndctl_pfn_is_enabled
    ndctl_pfn_get_region
    ndctl_pfn_enable
    ndctl_pfn_delete
    ndctl_pfn_is_configured

New utility commands:
    list
    help (man pages)
    create-namespace

Api fixes:
    ndctl_{namespace|btt}_foreach crash fix
    ndctl_namespace_delete no longer errors on "io" namespaces
    miscellaneous static analysis fixes

Utility command fixes:
    {en|dis}able-{namespace|region} return code