Many of the fatal errors in nm ought to be recoverable. This patch
downgrades most of them. The ones that are left are most likely due
to memory allocation failures.
* nm.c (print_symdef_entry): Don't bomb with a fatal error
on a corrupted archive symbol table.
(filter_symbols): Silently omit symbols that return NULL
from bfd_minisymbol_to_symbol rather than giving a fatal
error.
(display_rel_file): Don't give a fatal error on
bfd_read_minisymbols returning an error, or on not being able
to read dynamic symbols for synth syms.
(display_archive): Downgrade bfd_openr_next_archived_file
error.
(display_file): Don't bomb on a bfd_close failure.