Add a callback mechanism to autoload for "modules loaded" events.
Add a callback mechanism to autoload for "modules loaded" events.

lldb only supports a listener for each event at the moment. GALA uses
lldb.eBroadcastBitModulesLoaded to autoload gdb scripts, so we need
something like this in order to have another script that runs code on
module loads.

sivachandra/gala,sivachandra/gala