Add a new member to the end of the last manipulated struct/union.
arg1 The type of the new member.
arg2 The name of the new member.
[arg3] The array size. A value greater than zero will make this member an array.
[arg4] Offset from the start of the structure, only use this for implicitly padded structures. Overlapping with other members is not allowed.
This command does not set any result variables.