Implement `SSL_get_SSL_CTX` #150

Job	Run time
Clippy	34s
Clang Tidy	10s
Clippy nightly (optional)	32s
Build+test (stable, ubuntu-latest)	1m 41s
Check for documentation errors	41s
Build+test (beta, ubuntu-latest)	1m 32s
Format	17s
Miri	1m 2s
Build+test (nightly, ubuntu-latest)	1m 43s
Valgrind	1m 27s
Packaging	2m 24s
	12m 3s

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