Allow Command Prompt "copy" to handle file sizes up to almost 4 GB

Due to problems with the current Memory Manager, it is difficult to copy large files. This patch is a rough attempt to allow the Command Prompt "copy" to do this by using a 1 megabyte buffer over-and-over. Inspired by amber's comments and program in --CORE-13731--. This patch needs a developer to finish it up. I believe it to be working fairly well though now. Also I have attached cp6.c which I compiled in MinGW to its EXE which works from the Command Prompt.