PR binutils/2735

PR binutils/2735
* elflink.c (elf_link_add_object_symbols): Fix the warning message about
  mismatched alignments to allow for the case where the common alignment
  has been deduced from the section alignment.
* bfd.c (_bfd_default_error_handler): Update comment to explain why bfd
  and asection varargs are out of order.
  Explicitly catch and abort on NULL bfd and asection arguments.