updated changelog regarding foreign exception handling

Author: tomasstupka

CHANGELOG.md

@@ -5,6 +5,7 @@ New features:
 * interop and tooling: READ and WRITE of ActiveBinding may have side effects. This is communicated via `KEY_INFO` to the tools and other languages (e.g., a debugger may warn before evaluating an ActiveBinding)
 * the MRAN mirror used by FastR as default repo was moved to https://mran.microsoft.com/snapshot/2018-06-20
 * new function `install.fastr.packages` to install FastR rJava replacement and possibly other packages in the future
+* print the whole guest language stacktrace if an exception occurs during an interop call into another language
 
 Added missing R builtins and C API