Ensure that all forms of whitespace (en spaces, em spaces, etc) are handled by the backward/forward word delete functions

[steveluscher]

When you press fn-Option-delete on a Mac keyboard to delete a word, the OS counts leading whitespace as part of the range to be deleted. This must include other kinds of whitespace, other than just U+0020.

Repro:

1. Consider the string Hello\u2002World.
2. Place the caret after the word ‘Hello’
3. Press fn-Option-delete

The en space and the word ‘World’ should be deleted.

Then, consider all types of whitespace other than just \u2002.