tracer log method change for better support in waveform messaging tools
Created by: strichmo
Previous implementation of tracer emitted multiple fwrite calls to build a line in the trace log. This can cause line breaks in debug tools that log messages automatically (e.g. SmartLog in Indago, MessageViewer in Visualizer). This change accumulates line in a string variable and emits a single $fwrite.
The trace log should remain unchanged.