Uppercase converter

Converts everything to capitals. Unicode-aware, so accented letters convert properly rather than losing their accent.

The typographic argument against setting long passages in capitals is worth knowing: readers identify words partly by their outline, and capitals give every word the same rectangular shape, which measurably slows reading. Capitals are for short labels, headings and emphasis, not for paragraphs. On the technical side, uppercasing is not always a clean round trip — the German ß becomes SS and does not convert back, and in Turkish the dotless ı and dotted i uppercase differently. If the text is going into a system that will compare it, uppercasing and lowercasing are not equivalent ways to normalise it.