Move Broadcaster+Listener+Event combo from Core into Utility

Summary:
These are general purpose "utility" classes, whose functionality is not
debugger-specific in any way. As such, I believe they belong in the
Utility module.

This doesn't break any particular dependency (yet), but it reduces the
number of Core dependencies across the board.

Reviewers: zturner, jingham, teemperor, clayborg

Subscribers: mgorny, lldb-commits

Differential Revision: https://reviews.llvm.org/D55361

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@349157 91177308-0d34-0410-b5e6-96231b3b80d8
41 files changed