tests/all_tests.py: add local paths to the front of sys.path
tests/all_tests.py: add local paths to the front of sys.path

While doing pycparser development on a machine that already has an
older version of pycparser installed, we want unit tests to run against
the local copy instead of the system wide copy of pycparser.
This patch adds '.' and '..' to the front of sys.path instead of the back.

fjalex/pycparser,Nairolf21/pycparser,keulraesik/pycparser,jorik041/pycparser,keulraesik/pycparser,dubslow/pycparser,jorik041/pycparser,CtheSky/pycparser,CtheSky/pycparser,fjalex/pycparser,bowlofstew/pycparser,dementrock/pycparser,dubslow/pycparser,fjalex/pycparser,dubslow/pycparser,sideeffects/pycparser,bowlofstew/pycparser,dementrock/pycparser,strazzere/py010parser,Nairolf21/pycparser,sideeffects/pycparser,Nairolf21/pycparser,sideeffects/pycparser,strazzere/py010parser,dementrock/pycparser,sideeffects/pycparser,keulraesik/pycparser,CtheSky/pycparser,jorik041/pycparser,bowlofstew/pycparser