Introduce __bos0 as a #define for __builtin_object_size((s), 0).
This macro is intended to be used for places where the standard
__bos macro isn't appropriate.
memcpy, memmove, and memset deliberately use __bos0. This is done
for two reasons:
1) I haven't yet tested to see if __bos is safe to use.
2) glibc uses __bos0 for these methods.
Change-Id: Ifbe02efdb10a72fe3529dbcc47ff647bde6feeca
bd8e6749b7