Debugger: Implement remaining part of #11033.

TeamDebugInfo:
- Add function to invalidate a source entry's file mapping.
UserInterfaceListener:
- Add listener hook to be able to invoke the aforementioned invalidate.
  Add corresponding implementation in TeamDebugger.
FileManager:
- When asked to locate a source entry, invalidate any existing mapping
  first.
TeamWindow:
- Always allow choosing an alternate source file.
- If we already have an existing source mapping, invalidate it first
  before attempting to establish a new one.

src/apps/debugger/controllers/TeamDebugger.cpp

@@ -820,6 +820,15 @@ TeamDebugger::SourceEntryLocateRequested(const char* sourcePath,
 }
 
 
+void
+TeamDebugger::SourceEntryInvalidateRequested(LocatableFile* sourceFile)
+{
+	AutoLocker< ::Team> locker(fTeam);
+
+	fTeam->DebugInfo()->ClearSourceCode(sourceFile);
+}
+
+
 void
 TeamDebugger::FunctionSourceCodeRequested(FunctionInstance* functionInstance,
 	bool forceDisassembly)