Breakpad Mac dumper: Build cleanly as a 64-bit program.

Since we're using its types, #include <stdint.h>.

Don't cast 'void *' to 'uint32_t' where we need to do byte-pointer
arithmetic. Instead, use 'char *'; the language guarantees that
sizeof(char) == 1.

To make the above easier, pass pointers to byte buffers as 'char *', not
'void *.

Use natural pointer arithmetic where possible. If ptr is a 'struct A *', then
write:
        (struct B *) (ptr + 1)
instead of:
        (struct B *) ((char *) ptr + sizeof(struct A))
This helps us avoid (say) using the size of the 32-bit Mach-O header to
skip a 64-bit Mach-O header. (The latter has an extra 32-bit word at the
end.)

[jimb]

With this, I can build the dumper on a 64-bit platform.  I don't think it works,
though.

[jimb]

With the new Mac dumper patches I've just gotten working, this is obsoleted. 
Removing this from Neal's review queue.