tests/test-profile.out

run-tests.py: avoid using popen2.Popen4 - use subprocess instead

Use subprocess to emulate Popen4 if available - similar to how it is done in
util.py.

Using popen2 under python 2.6 gives
DeprecationWarning: The popen2 module is deprecated.  Use the subprocess module.

% test --time
% test --profile
% test --lsprof