fix for fixup_segment / MD_PCREL_FROM_SECTION

[law@redhat.com]

  In message < 20010829150419.G26936@bubble.sa.bigpond.net.au >you write:
  > On Tue, Aug 28, 2001 at 09:07:53PM +0100, Joern Rennecke wrote:
  > >   be made.  On many processors, the base of a PC relative instruction is 
  > the next
  > >   instruction, so this macro would return the length of an instruction.
  > > + @item TC_MD_PCREL_FROM_SECTION_FIXED
  > > + @cindexTC_MD_PCREL_FROM_SECTION_FIXED
  > > + You also need to define @code{TC_MD_PCREL_FROM_SECTION_FIXED} to make t
  > his
  > > + work right, because a large number of old ports papered over a bug in
  > > + fixup_segment by making the reverse error in their definition of
  > > + @code{MD_PCREL_FROM_SECTION}.
  > 
  > Hmm, alternatively, just modify the doco for MD_PCREL_FROM_SECTION to
  > reflect reality.  Note also that your patch misses a number of other
  > places where MD_PCREL_FROM_SECTION is used.
Ironic -- this is what I suggested to Joern privately when he indicated
that every port which uses MD_PCREL_FROM_SECTION was wrong according
to the documentation.

jeff