Problem: Message grid newline formatting based on `msg_col` is not
utilized with ext_messages.
Solution: Increment `msg_col` with the cell width of the chunk. Allowing
message code that uses `msg_col` to determine when to place a
newline to do so. E.g. when the message goes beyond `Columns`;
this is not necessarily where the ext_messages implementation
would want to place a newline, but it is a best guess. Message
parsing and manipulation is still possible.
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