Lint around file_ptr's (bfd's off_t's) and bfd_seek.

Lint around file_ptr's (bfd's off_t's) and bfd_seek.

* dbxread.c (read_dbx_symtab):  Use L_SET as bfd_seek arg.
(elfstab_build_psymtabs):  staboffset and stabstroffset args are
file_ptr's.
* dwarfread.c (struct dwfinfo):  Convert dbfoff, lnfoff to file_ptr.
(scan_compilation_units):  Punt unused filename arg.  dbfoff,
lnoffset, and curlnoffset are file_ptr's now.
(dwarf_build_psymtabs):  Drop desc and filename args; use
objfile.  dbfoff and lnoffset are file_ptr's now.
(read_ofile_symtab):  foffset is now file_ptr.  Use L_SET in bfd_seek.
* elfread.c (struct elfinfo):  dboffset and lnoffset are file_ptr's.
(elf_symfile_read):  Skip desc and filename args to
dwarf_build_psymtabs.  Pass file_ptr's to elfstab_build_psymtabs.
* gdb-stabs.h:  Use file_ptr rather than off_t.
* mipsread.c (fixup_symtab): f_ptr is a file_ptr.  Re-enable
compile-time debug check that someone turned off as "unused".
(read_the_mips_symtab):  st_filptr is a file_ptr.  Fix bfd_seek call.
* symfile.h:  Update dwarf_build_psymtabs and
elfstab_build_psymtabs prototypes.
* xcoffread.c (init_stringtab, init_lineno, xcoff_symfile_read):
Use file_ptr offsets.  bfd_seeks use L_SET.