Stop users accidently passing commands to the wrong process

[hardenedapple]

Given the nature of vsh, it's much easier to forget what process is currently running in the foreground (python, gdb, bc, etc) and send a previously used command to the wrong process.

This is usually harmless, but it could be avoided in a similar manner to how the current foreground process' working directory is stored with b:vsh_dir_store. We could write the current foreground process name on the command line and alert the user if they try to send something that originally went to a gdb process to a bash process.

Obviously, this would be optional.

I'm not sure I like this idea -- I'm writing it down here so I don't forget it, but have no plans to implement it as yet.