Split compat layer into different source files #506

Job	Run time
Ubuntu 20 GCC	45s
Ubuntu GCC ASAN	2m 19s
Ubuntu GCC UBSAN	2m 3s
Ubuntu GCC MSAN	58s
Ubuntu 20 Clang	42s
Ubuntu 20 Clang 6.0	59s
Ubuntu GCC	53s
Ubuntu GCC OSB	51s
Ubuntu Clang	1m 3s
Ubuntu Clang No Zlib	1m 0s
Ubuntu Clang No Bzip2	57s
Ubuntu Clang No LZMA	57s
Ubuntu Clang No Zstd	58s
Ubuntu Clang No Pkcrypt	1m 1s
Ubuntu Clang No Winzip AES	53s
Ubuntu Clang No Encryption	52s
Ubuntu Clang Compress Only	1m 2s
Ubuntu Clang Decompress Only	55s
Ubuntu Clang OpenSSL	1m 4s
Windows MSVC	3m 12s
Windows GCC Code Coverage	5m 34s
macOS Xcode	48s
macOS Xcode Code Coverage	55s
macOS Xcode LibCompression	55s
macOS Xcode OpenSSL	57s
	32m 33s

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