make the memcpy/memmove intrinsics higher-level

This allows them to make use of the type's alignment, instead of being
pessimistic and assuming it is only 1.
C++0x -> C++11
add memset32/memset64
use uninit for cast::transmute_copy
add an align parameter to call_memcpy
make transmute_copy use memcpy, and inline it
inline bump_box_refcount
fix casts on 32-bit