python tracing

[Stan Cox]

We test a variation of this in the upstream systemtap testsuite 
(testsuite/systemtap.apps/python.exp)  What the test does is: fetch 
upstream python sources, apply either one of python2.patch or 
python3.patch, build python, run test using a scenario similar to the 
following:

stap celsius-var.stp -c "python -sS celsius.py 30" '*' python.log
stap celsius-var.stp -c "python3 -sS celsius.py 30" '*' python.log