Dave Johnson 8a24ff94d1 AT90USB1286 PIO cleanup and optimization ()
-normalize `env` and `board` to lowercase naming convention.
-make board `name` follow descriptive convention.
-implement `-fsingle-precision-constant` compile optimization per https://github.com/MarlinFirmware/Marlin/pull/11178#issuecomment-401673901
-fix typo in 5DPRINT entry.
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at90usb1286.json AT90USB1286 PIO cleanup and optimization ()
malyanM200.json Add PIO board definitions for Malyan M200 ()
malyanM200v2.json Add PIO board definitions for Malyan M200 ()