py3: use print_function in silenttestrunner.py

py3: use absolute_import in silenttestrunner.py

py3: use print_function in hypothesishelpers.py

tests: use absolute_import in hypothesishelpers.py

py3: use print_function in get-with-headers.py

py3: use print_function in generate-working-copy-states.py

py3: use print_function in filterpyflakes.py

py3: use print_function in test-ancestor.py

py3: use print_function in seq.py

py3: use absolute_import in seq.py

parser: move parsererrordetail() function from revset module This will be used by common alias functions introduced by future patches.

hgweb: fix links in atom-branches

revset: prevent infinite recursion on pypy as explained in the commit, __len__ cannot do [x for x in self] because that can potentially call __len__ again, causing infinite recursion

pypy: fix doctests for pypy optimizations PyPy would sometime call __len__ at points where it things preallocating the container makes sense. Change the doctests so they're using generator expressions and not list comprehensions

largefiles: replace invocation of os.path module by vfs in reposetup.py This commit is part of bigger effort described in 'Windows UTF-8' plan.