0.4.0

Breaking changes

• Updated bitflags to 2.0.2, which changes the API of Attributes a bit.
• Updated map_range method to support mapping leaf page table entries without the VALID flag.
  Attributes::VALID is no longer implicitly set when mapping leaf page table entries.

New features

• Added modify_range method to IdMap, LinearMap and Mapping to update details of a mapped
  range. This can be used e.g. to change flags for some range which is already mapped. As part of
  this, the Descriptor struct was added to the public API.
• Added DBM and software flags to Attributes.