[docs] Glossary entry for __future__ module contradicts module's documentation

Compare: __future__: A *pseudo-module* which programmers can use to enable new language features which are not compatible with the current interpreter. (Glossary) and __future__ is a *real module*, and serves three purposes: ... (__future__ documentation) I suggest not to use pseudo/real module terminology and have two definitions for __future__ in glossary: one as a name of a module and the other as a keyword in the future statement.