This is more than cosmetic, it's also highly usable. The presence
or absence of the "ok" message allows us to know whether the command
aborted. Previously, the "> " prompt appeared when the system expected
a prompt in the INTERPRET context, whether the previous command aborted
or not.
Also, this allows us to get rid of that ugly FLAGS global variable.
This should help with the bootstrapping of non-emulated environment.
For example, I have a problem with the RC2014: I can't send it
bootstrap info until the ACIA is up. I need to find a way...