Server script to download the latest installer

As promised, I talked with enumag about the script and he sent it to me earlier today.

You can access it at http://07th-mod.com/installer.php

By default, it will guess the user platform and get the latest stable release. You can force it to go through manually using: ``http://07th-mod.com/installer.php?system=win|mac|linux&branch=pre|stable``

Example: http://07th-mod.com/installer.php?system=linux&branch=stable

Beware that using ``branch=pre`` will only work if the most recent release is marked as a pre-release. If the most recent is a stable release, it will get the stable instead of the pre-release.

Right now the guessing part doesn't work, but I believe it is because of the current changes ongoing at the releases page. Earlier today it was working fine, so it might fix itself soon enough.

O script está hospedado em http://07th-mod.com/installer.php e interage com os releases do GitHub. Comece examinando a lógica existente do lado do servidor para detecção de plataforma e busca de releases. Entenda como ele determina os branches 'stable' vs 'pre' e se integra com a página de releases do projeto. Teste o endpoint com diferentes parâmetros de consulta para verificar o comportamento atual e identificar o problema de adivinhação.

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