ENH: executable permissions for two scripts with shebangs

I haven't looked inside much yet so not sure if even changing appdirs submodule is warranted... but there are more files which seems were intended to be scripts and thus might like to become executable as well (after adding shebangs):

```
$> git grep -l  __main
cortex/freesurfer.py
cortex/mp.py
cortex/webgl/serve.py
scripts/dumpcmaps.py
scripts/sn_movie_make.py
```