Create array for mapping message Ids to proper structs

def generate_message_mappings_array(outf, msgs):
    """Create array for mapping message Ids to proper structs"""

    classes = []
    for msg in msgs:
        classes.append("%u: %s.self" % (msg.id, msg.swift_name))
    t.write(outf, """



/**
    Array for mapping message id to proper struct
*/
private let messageIdToClass: [UInt8: Message.Type] = [${ARRAY_CONTENT}]
""", {'ARRAY_CONTENT' : ", ".join(classes)})