Review core/std for bad copies

[brson]

After demoding there are going to be a number of argument parameters that should be by value instead of by reference and vice versa. In particular, any time a function wants to transform one thing into another it should probably take it by value and do moves, forcing the caller to decide about the copy.

[pcwalton]

Closing; most of these are gone now. Please open new issues with specific bugs.