Don't jump to source after commands that don't progress the program

[Charlie-83]

Currently (using gdb), typing a command like p foo will cause the program to jump to the source even thought the program hasn't progressed so it will jump to the same place each time. This is annoying when you want to print out a series of variable and you keep being taken out of the gdb terminal.

This PR stops this occurring by recording the previous filename + line we jumped to and only jumping if we are jumping somewhere else.

I have only implemented this for GDB (since it'' the only debugger I use). If there is interest in this PR, I can implement for the others.

[sakhnik]

Hi! Thanks for your interest. The change breaks some use cases. Specifically, when :Gdb run is executed after program exit. Could you reset the last known position when the program exits or restarts?

[Charlie-83]

I have fixed two cases.

1. The case you mentioned where you hit some breakpoint and then rerun the program and hit the same breakpoint
2. The breakpoint is in something like a loop so, after issuing continue you hit the same breakpoint again

[sakhnik]

I wonder why I can't reproduce the bug. Could you please record a small demo maybe in asciinema?

[Charlie-83]

What bug do you mean?

[sakhnik]

I didn't notice any unwanted jumps. Neither can I reproduce #213.

[Charlie-83]

https://asciinema.org/a/c7EpvcsNemBZOsMlBUptpxwRG

This is the behavior without this PR but with my patch for #213

#213 and this PR are separate. This PR is a feature while I think #213 is a bug. I haven't had time to look into #213 to find a reproducible case but I will get round to it soon. I will add an asciinema to it now though

[sakhnik]

Oh, right, I can reproduce this behaviour now, thanks!
I see the Windows test failed. I'll look at it over the weekend.