Expose zlib constants for backwards compat #529

Job	Run time
Ubuntu 20 GCC	55s
Ubuntu GCC ASAN	1m 27s
Ubuntu GCC UBSAN	17s
Ubuntu GCC MSAN	28s
Ubuntu 20 Clang	1m 24s
Ubuntu 20 Clang 6.0	1m 2s
Ubuntu GCC	26s
Ubuntu GCC OSB	22s
Ubuntu Clang	58s
Ubuntu Clang No Zlib	54s
Ubuntu Clang No Bzip2	54s
Ubuntu Clang No LZMA	1m 4s
Ubuntu Clang No Zstd	52s
Ubuntu Clang No Pkcrypt	57s
Ubuntu Clang No Winzip AES	43s
Ubuntu Clang No Encryption	52s
Ubuntu Clang Compress Only	56s
Ubuntu Clang Decompress Only	57s
Ubuntu Clang OpenSSL	17s
Windows MSVC	8s
Windows GCC Code Coverage	28s
macOS Xcode	58s
macOS Xcode Code Coverage	57s
macOS Xcode LibCompression	52s
macOS Xcode OpenSSL	1m 2s
	20m 10s

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