after-merge-snips (augmentable only) in text%

Called after adjacent snips in the editor are combined into one. See also merge-with

• (send a-text after-merge-snips pos) -> void
     pos : exact non-negative integer

  The pos argument specifies the position within the editor where the snips were merged (i.e., one old snip was just before pos, one old was just after pos, and the new snip spans pos).