Added the equivalent of gdb's "unwind-on-signal" to the expression command, and a parameter to control it in ClangUserExpression, and on down to ClangFunction.  

git-svn-id: https://llvm.org/svn/llvm-project/llvdb/trunk@118290 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/source/API/SBFrame.cpp b/source/API/SBFrame.cpp
index 1d90808..c0f2f55 100644
--- a/source/API/SBFrame.cpp
+++ b/source/API/SBFrame.cpp
@@ -560,11 +560,12 @@
         m_opaque_sp->CalculateExecutionContext (exe_ctx);
         
         const char *prefix = NULL;
+        const bool discard_on_error = true;
         
         if (exe_ctx.target)
             prefix = exe_ctx.target->GetExpressionPrefixContentsAsCString();
         
-        *expr_result = ClangUserExpression::Evaluate (exe_ctx, expr, prefix);
+        *expr_result = ClangUserExpression::Evaluate (exe_ctx, discard_on_error, expr, prefix);
     }
     
     if (log)