[docs] sys.maxunicode documentation is imprecise

[Alexander Belopolsky]

"""
sys.maxunicode

An integer giving the largest supported code point for a Unicode
character. The value of this depends on the configuration option that
specifies whether Unicode characters are stored as UCS-2 or UCS-4.
""" http://docs.python.org/dev/library/sys.html#sys.maxunicode

The term "Unicode character" is imprecise.   A better term is "Unicode
code unit" as used in  Data model/Sequences/Strings section.

Also "sys.maxunicode" is not hyperlinked in Data model page.

http://docs.python.org/dev/reference/datamodel.html#objects-values-and-types