Remove char::to_titlecase?

[brson]

Converting a string to titlecase requires a word-breaking algorithm, which std does not provide. We do have the method for converting a single char to titlecase, if one can identify the first char of a word. This method requires a few kb of lookup tables.

We might want to consider whether its wise to ship one without the other. This is marked for stabilization in 1.2 so we need to decide soon.

cc @SimonSapin @alexcrichton @aturon

[alexcrichton]

This is marked for stabilization in 1.2 so we need to decide soon.

The method is marked as unstable so I'm fine just deleting it, I don't think it's marked to be stable.