Thread hardening part 3. Now lldb_private::Thread objects have std::weak_ptr
objects for the backlink to the lldb_private::Process. The issues we were
running into before was someone was holding onto a shared pointer to a 
lldb_private::Thread for too long, and the lldb_private::Process parent object
would get destroyed and the lldb_private::Thread had a "Process &m_process"
member which would just treat whatever memory that used to be a Process as a
valid Process. This was mostly happening for lldb_private::StackFrame objects
that had a member like "Thread &m_thread". So this completes the internal
strong/weak changes.

Documented the ExecutionContext and ExecutionContextRef classes so that our
LLDB developers can understand when and where to use ExecutionContext and 
ExecutionContextRef objects.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@151009 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/source/Commands/CommandObjectBreakpointCommand.cpp b/source/Commands/CommandObjectBreakpointCommand.cpp
index 7283e6d..a7e98ea 100644
--- a/source/Commands/CommandObjectBreakpointCommand.cpp
+++ b/source/Commands/CommandObjectBreakpointCommand.cpp
@@ -799,7 +799,8 @@
     
     if (commands.GetSize() > 0)
     {
-        Target *target = context->exe_ctx.GetTargetPtr();
+        ExecutionContext exe_ctx (context->exe_ctx_ref);
+        Target *target = exe_ctx.GetTargetPtr();
         if (target)
         {
             CommandReturnObject result;
@@ -817,7 +818,7 @@
             bool print_results    = true;
 
             debugger.GetCommandInterpreter().HandleCommands (commands, 
-                                                             &(context->exe_ctx),
+                                                             &exe_ctx,
                                                              stop_on_continue, 
                                                              data->stop_on_error, 
                                                              echo_commands,