Assumtion that uppercase and lowercase versions of characters are confusable

[JennyLynnFletcher]

In parse.py when creating the confusable sets, there is an assumption that if a certain character is confusable with another, it will also be confuseable with the upper/lower case version. This isn't always the case.

For example this causes "latin small letter v" (v) to be confusable with "latin capital letter n" (N), as "greek small letter nu" is confusable with "latin small letter v" (03BD) and calling string.upper() on charater 03BD produces "latin capital letter n".