The lineno and col_offset attributes of AST nodes for list comprehensions,
generator expressions and tuples are now point to the opening parenthesis or
square brace. For tuples without parenthesis they point to the position
of the first item.
There are some same consts in a module. This commit merges them into
single instance. It reduces number of objects in memory after loading modules.
https://bugs.python.org/issue34100
Current support for hash-based bytecode files in `zipimport` is rather
sparse, which leads to test failures when the test suite is ran with
the ``SOURCE_DATE_EPOCH`` environment variable set.
This teaches zipimport to handle hash-based pycs properly.
