x11/xscreensaver: Adopt and clean up

Take maintainership as discussed with manu via email. Also clean up:

- Remove USES=desktop-file-utils again, the desktop files don't register
  any MIME types
- Add USES=shebangfix to fix the perl shebang, remove manual patching
- Remove MAKE_JOBS_UNSAFE, parallel builds seem to work just fine
- Format according to portclippy recommendations
- Update local patches

Approved by:	x11 (manu)