2to3: Apply renames fixer.

Rename sys.maxint to sys.maxsize when the Python version is >= 3.  This
change was made in Python 3 because all integers are 'long' integers and
their maximum value bears no relationship to the C type that int used to
represent. The new sys.maxsize value is the maximum value of Py_ssize_t.
This change has not led to any reported problems since the numpy 1.5
release.

Closes #3082