* nm.c: Include libiberty.h.
(sort_by_size): New static variable.
(long_options): Add --size-sort.
(usage): Mention --size-sort.
(numeric_forward): Make static. Change from void * to PTR.
(numeric_reverse): Likewise.
(non_numeric_forward, non_numeric_reverse): Likewise.
(sorters): Change declaration from void * to PTR.
(size_forward, sort_symbol_by_size): New static functions.
(display_rel_file): Handle sort_by_size.
(filter_symbols): If sort_by_size, discard absolute and undefined
symbols.
* binutils.texi (nm): Document --size-sort.
* nm.1: Document --size-sort.
PR 3611.