Fix bfd_read to cope with bad BIMs

[Ian Lance Taylor]

   Date: Fri, 21 Jan 2000 10:33:49 -0800
   From: Nick Clifton <nickc@cygnus.com>

     The patch below fixes a small bug in bfd_read().  If a bfd_in_memory
     structure has a "size" field that is less than the value of
     "abfd->where" then the code would attempt to memcpy() a negative sized
     amount of data, resulting in a segmentation fault.

     Is this patch OK to apply ?

Yes, but there is probably another bug.  bfd_seek should not let you
set the abfd->where field of a BFD_IN_MEMORY BFD to an invalid value.

Ian