Added "void Clear();" methods to SBDebugger, SBTarget and SBThread so they can release their shared pointers.

git-svn-id: https://llvm.org/svn/llvm-project/llvdb/trunk@109882 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/source/API/SBDebugger.cpp b/source/API/SBDebugger.cpp
index 84856ef..a07a8ae 100644
--- a/source/API/SBDebugger.cpp
+++ b/source/API/SBDebugger.cpp
@@ -43,6 +43,12 @@
     Debugger::Terminate();
 }
 
+void
+SBDebugger::Clear ()
+{
+    m_opaque_sp.reset();
+}
+
 SBDebugger
 SBDebugger::Create()
 {