Found one more place where the OkayToDiscard needs to be consulted.
Also changed the defaults for SBThread::Step* to not delete extant plans.
Also added some test cases to test more complex stepping scenarios.

llvm-svn: 156667
diff --git a/lldb/scripts/Python/interface/SBFrame.i b/lldb/scripts/Python/interface/SBFrame.i
index 4bedbff..20093a0 100644
--- a/lldb/scripts/Python/interface/SBFrame.i
+++ b/lldb/scripts/Python/interface/SBFrame.i
@@ -137,6 +137,9 @@
     lldb::SBValue
     EvaluateExpression (const char *expr, lldb::DynamicValueType use_dynamic);
 
+    lldb::SBValue
+    EvaluateExpression (const char *expr, lldb::DynamicValueType use_dynamic, bool unwind_on_error);
+
     %feature("docstring", "
     /// Gets the lexical block that defines the stack frame. Another way to think
     /// of this is it will return the block that contains all of the variables