Add #self, #Self to #function, #file, #line, #column

[thomasvl (Thomas Van Lenten)]

@sindresorhus

I would also like to see #file become a relative path.

The value depends on what was passed when swiftc was invoked. Changing it (and having it honor some options) has come up a few times. Some likely related threads:

• Change value of #file literal for release builds
• Modifying debug info for hermetic/distributable builds
• [Question] Absolute paths in executable .swiftmodule files