Added SWI instruction for ARM.
Added support for <require> command (feature sets).
Added convenience methods [cpudl].Context.parseStringAttribute and parseIntegerAttribute.
Added support for <prefix> element.
Added support for negated features in <require> element.
Added support for IX and IY addressing modes for Z80, fixing errors with opcodes 22H and 2AH.
Corrected errors in RLD and RRD instruction effects for Z80.