jeffnye-gh/dromajo_stf_update (#119)

improve performance when stf tracing is enabled, issue #55 
 
retain n_cycles=10000 until the stf trace opc is detected. 
Once the stop opc is detected restore n_cycles=10000

result is better interactivity under linux, improving overall
performance and usability when not actively generating a trace.

This is a re-implementation of previous draft PR.

trace opc trigger detection is done in dromajo_template.
trace record creation and handling is done in dromajo_stf.cpp
headers gathered into dromajo_stf.h

---------

Co-authored-by: jeff <jeffnye-gh@github.com>