test.test_support.import_module().

Merged r62778, r62779, r62802, r62806, r62807, r62808, r62809, r62844,
r62846, r62952, r62956.

negative; fix to return an (appropriately signed) zero instead.

could be incorrectly raised.  This is a backport of the
Py3k fix in r62939.  (Should really have been fixed
in the trunk first and svnmerged into py3k.)

Uncomment PEP 370 section.
Add some module items

unclear whether the verbatim text should have been indented or by how much.

Closes issue #2790.