variant: extended API to support (optional) referenced strings and bytes #159

Job	Run time
CentOS 7 build to confirm no issues once used downstream	1m 8s
Build with various code analysis tools (clang-sanitize-address)	26s
Build with various code analysis tools (clang-sanitize-memory)	32s
Debian Buster build to confirm no issues once used downstream	28s
Build with various code analysis tools (clang-sanitize-undefined)	21s
Build sources on MSYS2 for windows-latest	1m 57s
Build with various code analysis tools (clang-sanitize-dataflow)	30s
Build sources on amd64 for ubuntu-latest - gcc	12s
Build sources on MSYS2 for windows-2019	1m 35s
Build with various code analysis tools (clang-sanitize-safe-stack)	24s
Build sources on amd64 for ubuntu-latest - clang	30s
Build with various code analysis tools (valgrind)	25s
Build sources on arm64 for ubuntu-latest - gcc	3m 1s
Build sources on arm64 for ubuntu-latest - clang	2m 49s
Build sources on amd64 for macos-latest - gcc	44s
Build sources on amd64 for windows-latest	11s
Build sources on amd64 for macos-latest - clang	17s
Build sources on amd64 for windows-2019	1m 2s
	16m 32s

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