disambiguate Main modules

[bergey]

I'm using graphmod on several packages that define multiple executables, each module implicitly named Main. graphmod does a fine job when each executable has an explicit (unique) module declaration, or when there is only one Main. With multiple Mains, I'm not getting edges drawn for any of them.

Would you add a feature to better handle multiple Main modules?

I have a few ideas of what this might look like:

• when encountering multiple Mains, automatically substitute file name
• same as above, but only with a command line option
• same as above, but prepend file name, like filename:Main
• same as above, only for files without explicit module declaration

Any of these would meet my needs.