Fix merging of adjacent hunks in SpliceOld
Fix merging of adjacent hunks in SpliceOld

* Concatenate the text of merged nodes
* Null out the left child of deleted node before deleting the node.

Signed-off-by: Max Brunsfeld <78036c9b69b887700d5846f26a788d53b201ffbb@github.com>

atom/superstring,atom/superstring,atom/superstring,atom/superstring,atom/superstring