Merge devo/bfd with GDB's bfd.

Merge devo/bfd with GDB's bfd.

Remove obstack.h to ../include and obstack.c to ../libiberty.
Move COFF symbol swapping code to coffswap.c where GDB can call it but it
won't be duplicated if we have N different COFF targets.
Add support for traditional Unix core files (with a upage).  This support
is from an Ultrix port, but is probably slightly broken now.
Improve bfd_release's of obstack'd items on error returns.
gcc -Wall fixes.
Handle section alignment slightly better in coff, and comment where it
needs more work (on page-aligning virtual vs file addresses for DPAGED).
Use set_tdata everywhere that tdata is set, to avoid "cast to the left
of assignment" problems with some compilers.
Move bfd_alloc, bfd_zalloc, bfd_realloc, and bfd_release into libbfd.h
(from bfd.h) since they are internal routines.
Remove the redundant suffix "_struct" from struct tags.
Set symbol count early in file reading, before slurping in the syms,
for GDB's use.