Add SSL_CTX_dup API #72

Job	Run time
basic_clang	7m 30s
basic_gcc	7m 39s
address_ub_sanitizer	15m 8s
buildtest	11m 10s
check_docs	1m 17s
check_update	2m 4s
check-ansi	4m 28s
enable_brotli_and_asan_ubsan	13m 6s
enable_brotli_and_zstd_dynamic	7m 10s
enable_brotli_dynamic	7m 25s
enable_non-default_options	8m 7s
enable_zstd_and_asan_ubsan	14m 22s
enable_zstd_dynamic	7m 37s
enable-tfo (ubuntu-latest)	9m 13s
external-test-cf-quiche	7m 29s
enable-tfo (macos-latest)	10m 50s
external-test-pyca (1.51.0, 3.9)	12m 0s
external-tests	13m 48s
legacy	5m 47s
memory_sanitizer	19m 1s
minimal	3m 29s
fips_and_ktls	9m 29s
no-deprecated	7m 23s
non-caching	20m 52s
no-legacy	7m 36s
no-shared (ubuntu-latest)	7m 8s
out-of-source-and-install (ubuntu-latest)	12m 0s
no-shared (macos-latest)	8m 29s
threads_sanitizer	6m 46s
out-of-source-and-install (macos-latest)	10m 21s
	4h 38m 44s

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