Change premake.extensions namespace to premake.modules, to match online docs

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extra : rebase_source : 3906398e7a3cb5cb47ab23e8f577d04623b0fffc
Add api.alias() to allow complete aliasing of project API calls

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extra : rebase_source : af24d115d30b6d7213b8e2c0b11b9110cee2a829