librnd 4.0.0
~~~~~~~~~~~~

Major, API breaking release that implements pending API fixes, extensions
and cleanups that could not be done within librnd3 without breaking
compatibility.

Feature highlights:

- support for handling multiple designs
- support for tracking design-project relation
- import pcb-rnd's generalized font lib into librnd API
- split core from hid; it is possible to link to the core part of librnd
  without linking to any of the hid API
- dynamic unit system: applications can register their units and unti families
- relax drawing area assumptions/limitations: drawing area is defined with
  a box and accepts negative coords
- DAD: it is mandatory to name panes; saving and restoring window geometry
  always includes panes
- clean up terminology in API names: use "design" instead of hidlib or pcb or
  board
- HID API simplification: remove beep() and always assume textual data
  on clipboard, centralized mouse cursor management, centralized busy(),
  remove faded drawing (callee can just use different color)
- import utils from pcb-rnd and install them so that apps don't need to
  keep local copies (mainly build related scripts)