cfl: add new cfl_version() and unit tests #163

Job	Run time
CentOS 7 build to confirm no issues once used downstream	1m 6s
Debian Buster build to confirm no issues once used downstream	30s
Build with various code analysis tools (clang-sanitize-address)	20s
Build with various code analysis tools (clang-sanitize-memory)	21s
Build sources on MSYS2 for windows-latest	1m 40s
Build with various code analysis tools (clang-sanitize-undefined)	19s
Build sources on amd64 for ubuntu-latest - gcc	8s
Build sources on MSYS2 for windows-2019	1m 40s
Build with various code analysis tools (clang-sanitize-dataflow)	19s
Build sources on amd64 for ubuntu-latest - clang	9s
Build with various code analysis tools (clang-sanitize-safe-stack)	21s
Build sources on amd64 for macos-latest - gcc	12s
Build with various code analysis tools (valgrind)	21s
Build sources on amd64 for macos-latest - clang	11s
Build sources on arm64 for ubuntu-latest - gcc	2m 49s
Build sources on arm64 for ubuntu-latest - clang	2m 49s
Build sources on amd64 for windows-latest	11s
Build sources on amd64 for windows-2019	33s
	13m 59s

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