* backtrace.h (backtrace_syminfo_callback): Add symsize argument.
* elf.c (elf_syminfo): Pass 0 or sym->size to the callback as
last argument.
* btest.c (struct symdata): Add size field.
(callback_three): Add symsize argument. Copy it to the data->size
field.
(f23): Set symdata.size to 0.
(test5): Likewise. If sizeof (int) > 1, lookup address of
((uintptr_t) &global) + 1. Verify symdata.val and symdata.size
values.