Initial Curve448 implementation #928

Job	Run time
mypy	17s
build_python_27 (ubuntu-20.04, yes)	2m 31s
python_no_gil	2m 55s
build_python_27 (ubuntu-20.04, no)	2m 28s
build (3.6, yes, ubuntu-20.04)	2m 27s
build_python_27 (windows-latest, yes)	3m 58s
test_c_linux (0, x64)	51s
build_python_27 (windows-latest, no)	4m 16s
build (3.6, no, ubuntu-20.04)	2m 22s
test_c_windows (x64)	32s
test_c_linux (0, x32)	59s
test_c_windows (win32)	56s
test_c_linux (1, x64)	1m 16s
test_c_linux (1, x32)	1m 6s
build (3.7, yes, ubuntu-20.04)	2m 20s
build (3.7, no, ubuntu-20.04)	2m 19s
build (3.8, yes, ubuntu-20.04)	2m 13s
build (3.8, no, ubuntu-20.04)	2m 14s
build (3.9, yes, ubuntu-20.04)	2m 12s
build (3.9, no, ubuntu-20.04)	2m 10s
build (3.10, yes, ubuntu-20.04)	2m 6s
build (3.10, no, ubuntu-20.04)	2m 7s
build (3.11, yes, ubuntu-20.04)	1m 50s
build (3.11, no, ubuntu-20.04)	1m 52s
build (3.12, yes, ubuntu-20.04)	1m 55s
build (3.12, no, ubuntu-20.04)	2m 3s
build (3.13-dev, yes, ubuntu-20.04)	1m 54s
build (3.13-dev, no, ubuntu-20.04)	2m 9s
build (3.12, yes, macos-12)	2m 59s
build (3.12, no, windows-latest)	3m 32s
build (3.12, yes, windows-latest)	3m 59s
build (pypy2.7, no, ubuntu-latest)	1m 25s
build (pypy3.9, no, ubuntu-latest)	1m 34s
	1h 9m 47s

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