Check overwrite of file

[jwilberding]

If receiving file, check to make sure not overwriting, if it will, ask user first.

[kaoru]

Seconded! My first test of bcp was to try it locally:

$ ./bcp /path/to/file &
$ ./bcp 

Two unexpected things happened:

1. bcp copied the file to /path/to/file. I expected the file to be copied into my current working directory on the receiving side.
2. bcp didn't warn me that it would immediately empty the file I was copying

[jwilberding]

Also added overwrite prompt with ab1c5ec

[kaoru]

Nice! Thanks :-)