p_memcpy implementation

[indrora]

p_memcpy(void*, void*, int, int) needs to be implemented.

There's a lot of implementations of memcpy -- newlib has a fantastically huge one for each platform.

Some notes from the source:

 * 0. User space
 * 1. Specific to bsb/device/os
 * 2. Should be lightning fast
 * 3. Add "safety" compile switch for error checking
 * 4. Function should not call any
 * 5. Need a different call per chip, board, O/S?

and some personal observations:

1. Of course it's userspace.
2. Why? How? (If it's specific to a bsp/dev/os, shouldn't it be dev_ops?)
3. This needs to be clearly defined; newlib variants can be found with fantastical memcpy implementations, optimizing for all sorts of things, and OpenBSD has it in libkern.
4. How should this be named? Kernel style doesn't dictate those names (as I can tell). I would rather a compile flag along the lines of FAIL_FAST but others would name it __SAFE_MEMCPY.
5. Did Candlejack come b--
6. Should this be a special thing? (also, somewhat contradicts item 1)

Memcpy isn't a terribly special function, but gets a lot of press for being a pusher of bits.