The debugger's API mode added a lot of extra complexity to the debugger client for minimal value. It also had a bunch of bugs, and unnecessarily tied alternate debugger clients to the command line client implementation. Deleting it.
Differential Revision: D912729
The = command uses formatting that is user customizable and subtly different, by default, from the formatting used by the print command and the variable command. This has historical roots. It seems that the debugger used to use print_r, which is brittle, and the customization hook was introduced to work around this brittleness. This work around is no longer necessary since the debugger now has its own, robust way of formatting values as strings. Also, the difference between = and print is a perennial source of confusion for debugger users.
Mike Magruder