loongson/pypi: links for plainmp

loongson/mirror plainmp-0.3.4.tar.gz
loongson/mirror plainmp-0.3.3.tar.gz
loongson/mirror plainmp-0.3.2.tar.gz
loongson/mirror plainmp-0.3.1.tar.gz
loongson/mirror plainmp-0.3.0.post1.tar.gz
loongson/mirror plainmp-0.2.3.tar.gz
loongson/mirror plainmp-0.2.2.tar.gz