On 32-bit targets, memory requested for program/section headers on a
fuzzed binary can wrap to 0. A bfd_alloc of zero bytes actually
returns a one byte allocation rather than a NULL pointer. This then
leads to buffer overflows.
Making this check unconditional triggers an extremely annoying gcc-5
warning.
PR19323
* elfcode.h (elf_object_p): Check for ridiculous e_shnum and
e_phnum values.