lib: Expose runtime.handleMessage again
lib: Expose runtime.handleMessage again

noflo-runtime still relies on it

microflo/microflo,microflo/microflo,rraallvv/microflo,microflo/microflo,microflo/microflo,rraallvv/microflo,rraallvv/microflo,rraallvv/microflo,microflo/microflo,microflo/microflo