Expose zlib constants for backwards compat #530

Job	Run time
Ubuntu 20 GCC	51s
Ubuntu GCC ASAN	2m 19s
Ubuntu GCC UBSAN	1m 59s
Ubuntu GCC MSAN	47s
Ubuntu 20 Clang	44s
Ubuntu 20 Clang 6.0	1m 30s
Ubuntu GCC	52s
Ubuntu GCC OSB	52s
Ubuntu Clang	58s
Ubuntu Clang No Zlib	1m 0s
Ubuntu Clang No Bzip2	55s
Ubuntu Clang No LZMA	57s
Ubuntu Clang No Zstd	53s
Ubuntu Clang No Pkcrypt	1m 8s
Ubuntu Clang No Winzip AES	50s
Ubuntu Clang No Encryption	38s
Ubuntu Clang Compress Only	56s
Ubuntu Clang Decompress Only	46s
Ubuntu Clang OpenSSL	1m 5s
Windows MSVC	3m 21s
Windows GCC Code Coverage	6m 15s
macOS Xcode	50s
macOS Xcode Code Coverage	52s
macOS Xcode LibCompression	1m 7s
macOS Xcode OpenSSL	51s
	33m 16s

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