Vim provides updates to major release through source patches, we don't want those in src/
since we didn't create them. With patchdir we can easily control where patches should be located.
Made clean() tell what it does.
I've added more helper functions to make it easier to override the functionality of the generic_*
functions. Breaking them down into smaller functions should make it easier to just replace a part of them
in the pr. package script.
