* libbfd.c (bfd_read): Set bfd_error as appropriate for a short

    * libbfd.c (bfd_read): Set bfd_error as appropriate for a short
        read. (bfd_error_system_call or bfd_error_file_truncated).

        * som.c: Do not blindly set bfd_error_system_call after a
        failing bfd_read, bfd_write, or bfd_seek.  In a few places
        (like som_object_p) override the error status set by bfd_read.

        * aix386-core.c, aout-encap,c archive.c, bout.c: Likewise.
        * coff-rs6000.c, coffgen.c ecoff.c, elf.c: Likewise.
        * elf32-hppa.c, elfcode.h, hp300hpux.c, i386lynx.c: Likewise.
        * nlm32-alpha.c, nlm32-i386.c, nlm32-sparc.c: Likewise.

        * som.c: Check return values from several bfd_{seek,read,write}
        calls that we just assumed were not failing.