Paul Sokolovsky d720ab5236 Implement modules as singletons Python semantics.
In Python, importing module several times returns same underlying module
object. This also fixes import statement handling for builtin modules.

There're still issues:
1. CPython exposes set of loaded modules as sys.modules, we may want to
do that either.
2. Builtin modules are implicitly imported, which is not really correct.
We should separate registering a (builtin) module and importing a module.
CPython keeps builtin module names in sys.builtin_module_names .
2014-01-20 00:38:39 +02:00
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2014-01-19 01:40:47 +02:00