interpolate {msg} in default LayoutGlue spec

[mmuurr]

Fairly(?) sure the default layout spec in the LayoutGlue initializer should have {msg} instead of msg.

[s-fleck]

Thanks. I guess noone used this before ;)

[mmuurr]

Or perhaps it was used, but folks were perfectly happy with simply msg as the msg, which is a nice way to get rid of those pesky error messages :-)