installation information tweaks

[Jeffrey A Law]

  In message < 199709061819.OAA18569@tweedledumb.cygnus.com >you write:
  > 	* fixincludes: Add a hack to the big sed script to work around a
  > 	bug in the sed implementation on HP/UX 10.20.
  > 
  > 
  > What is the bug that you are discussing here?  Would it be possible to
  > work around it?
I believe David is referring to the same problem that we worked around
in fixincludes (and various configure scripts) and, therefore the docs
really aren't necessary.

Also, HP has released a patch for hpux10.20 sed which fixes all of these
problems.

jeff