loongson/pypi: links for metalang

loongson/mirror metalang-0.52.tar.gz
loongson/mirror metalang-0.51.tar.gz
loongson/mirror metalang-0.50.tar.gz
loongson/mirror metalang-0.49.tar.gz
loongson/mirror metalang-0.49b.tar.gz
loongson/mirror metalang-0.48a.tar.gz