In PoseMode, the Ctrl-A hotkey can now be used to apply the current pose as the new restpose for the armature.
Notes:
* Roll correction may not be totally correct on bone chains, but is ok in most cases.
* Objects that are bone parented to the armature where this is applied are not correctly adjusted yet.
* It is advisable to 'apply' the existing armature deformations to geometry deformed by the armature before applying this, to prevent unexpected results.
* No menu entry yet... will add in due course.