Backport PR
#2554: Avoid stopping in ipdb until we reach the main script....
Backport PR
#2554: Avoid stopping in ipdb until we reach the main script.
For example:
```
In [1]: %run -d -b 52 setup.py
Breakpoint 1 at /tmp/ipython/setup.py:52
NOTE: Enter 'c' at the ipdb> prompt to start your script.
> /tmp/ipython/setup.py(7)<module>()
6 Under Windows, the command sdist is not supported, since IPython
----> 7 requires utilities which are not available under Windows."""
8
```
compared to the previous behavior:
```
In [1]: %run -d -b 52 setup.py
Breakpoint 1 at /tmp/ipython/setup.py:52
NOTE: Enter 'c' at the ipdb> prompt to start your script.
> <string>(1)<module>()
```
Closes
#1679 ("List command desn't work in ipdb debugger the first time")
