[NTG-context] Latin setupmathematics

In order to align with Unicode, \setupmathematics might have Latin shape options, as the Greek ‘lcgreek’ and ‘ucgreek', say ‘lclatin' and ‘uclatin', both defaulting to ’italic’. Unicode added the Latin italic symbols to the Math Alphanumeric Symbols range, so the upright letters are inaccessible when italic is assigned to the Basic Latin (ASCII) range.