beta-7

This marks the end of the short but very intensive development cycle
with lots of changes to freedos. Over 50 commits in 3 weeks.
Lots of regressions were introduced and are hopfully all now fixed,
so the release tagging is a due.

• Lots of work on fdkernel to use far pointers for data access. [fdkernel]
  This allows to relocate the fdpp memory pool to UMB.
  Unfortunately freedos can't yet re-use the freed space.
• Fixes to relocation code for more source-level compatibility [fdpp]
  with freedos.
• Fixed long-standing bug that caused the excessive size of the [fdkernel]
  realmode kernel image. Now realmode part shrunk by 4k (from
  15 to 11k). Certainly that sets a record for the world-smallest
  realmode part of any available DOS.
• Thunk templates are no longer hand-written. They are now [fdpp]
  generated by the use of m4sugar aka autoconf. We are likely
  the first project to use autoconf not to generate configure
  but rather for meta-programming.
• Set of bug fixes, both reported and found during code review.
  Code review is mostly over, so we are well set towards the
  stable releases hopefully (after a few more betas).