Fix std.uni.toUpper

[DmitryOlshansky]

This changes few badly generated tables that are used in toUpper/toLower breaking toUpper in some cases.

Apparently 9629 was fixed with new std.uni, this pull adds a test case for it.

[quickfur]

Why is toLower("\u1E9E")=="\u00df") but toUpper("\u00df")=="SS"? Is this according to the Unicode spec?

Other than that, LGTM.

[monarchdodra]

Is this according to the Unicode spec?

Yeah, it's one of those special cases. Unicode makes no promise that the upper case of a character is the uppercase of the lower case. This is because of a "N uppercase version to 1 lower case version".

Also, any letter that is "capital case" may expose similar "odd" behavior. Though to be honest, ẞ really is exceptional in this regard.

[DmitryOlshansky]

Why is toLower("\u1E9E")=="\u00df") but toUpper("\u00df")=="SS"? Is this according to the Unicode spec?

By spec. In general composition of toUpper.toLower may permute a string that was all lowercase, ditto with toLower.toUpper.

[quickfur]

Ah, another one of those Unicode complexities. Fair enough. LGTM. :)

[monarchdodra]

Closing as this is superseded by the pulled #1594 .