Swift 4.2 syntax

[timojaask]

Tried to convert to Swift 4.2 syntax. This is a bit scary since there are no tests, but most of the changes are just renaming things, so should be ok. The only part where I had to refactor a bit more is the following:

processEditing was using NSTextStorageEditActions for both platforms, like so:

override func processEditing(for textStorage: NSTextStorage, edited editMask: NSTextStorageEditActions, range newCharRange: NSRange, changeInLength delta: Int, invalidatedRange invalidatedCharRange: NSRange) {
	super.processEditing(for: textStorage, edited: editMask, range: newCharRange, changeInLength: delta, invalidatedRange: invalidatedCharRange)
	if invalidatedCharRange.location < lastParaLocation {
		//  When the backing store is edited ahead the cached paragraph location, invalidate the cache and force a complete
		//  recalculation.  We cannot be much smarter than this because we don't know how many paragraphs have been deleted
		//  since the text has already been removed from the backing store.
		lastParaLocation = 0
		lastParaNumber = 0
	}
}

However, it seems that in 4.2 it was renamed to NSTextStorage.EditActions on iOS platform, but not on macOS. So I decided to refactor it like this:

#if os(macOS)
override func processEditing(for textStorage: NSTextStorage, edited editMask:NSTextStorageEditActions, range newCharRange: NSRange, changeInLength delta: Int, invalidatedRange invalidatedCharRange: NSRange) {
    super.processEditing(for: textStorage, edited: editMask, range: newCharRange, changeInLength: delta, invalidatedRange: invalidatedCharRange)
    processEditing(invalidatedCharRange: invalidatedCharRange)
}
#else
override func processEditing(for textStorage: NSTextStorage, edited editMask:NSTextStorage.EditActions, range newCharRange: NSRange, changeInLength delta: Int, invalidatedRange invalidatedCharRange: NSRange) {
    super.processEditing(for: textStorage, edited: editMask, range: newCharRange, changeInLength: delta, invalidatedRange: invalidatedCharRange)
    processEditing(invalidatedCharRange: invalidatedCharRange)
}
#endif

func processEditing(invalidatedCharRange: NSRange) {
    if invalidatedCharRange.location < lastParaLocation {
        //  When the backing store is edited ahead the cached paragraph location, invalidate the cache and force a complete
        //  recalculation.  We cannot be much smarter than this because we don't know how many paragraphs have been deleted
        //  since the text has already been removed from the backing store.
        lastParaLocation = 0
        lastParaNumber = 0
    }
}

Hopefully this makes sense.