Apply SF patch #101135, adding 'import module as m' and 'from module import

Apply SF patch #101135, adding 'import module as m' and 'from module import
name as n'. By doing some twists and turns, "as" is not a reserved word.

There is a slight change in semantics for 'from module import name' (it will
now honour the 'global' keyword) but only in cases that are explicitly
undocumented.