Improved performance of "all files" setting

[robotboy655]

Use glualinter's ability to lint multiple files at once to severely cut down on number of processes spawned.

For GMod's base Lua code, the number goes from 619 to around 60, which significantly improves performance on Windows.

Related discussion: https://github.com/FPtje/GLuaFixer/issues/175

[Goz3rr]

Thanks 👍