variant: extended API to support (optional) referenced strings and bytes #160

Job	Run time
CentOS 7 build to confirm no issues once used downstream	1m 19s
Build with various code analysis tools (clang-sanitize-address)	23s
Build with various code analysis tools (clang-sanitize-memory)	27s
Debian Buster build to confirm no issues once used downstream	25s
Build with various code analysis tools (clang-sanitize-undefined)	22s
Build sources on MSYS2 for windows-latest	1m 39s
Build with various code analysis tools (clang-sanitize-dataflow)	25s
Build sources on MSYS2 for windows-2019	2m 4s
Build sources on amd64 for ubuntu-latest - gcc	6s
Build sources on arm64 for ubuntu-latest - gcc	2m 58s
Build with various code analysis tools (clang-sanitize-safe-stack)	21s
Build sources on amd64 for ubuntu-latest - clang	17s
Build sources on arm64 for ubuntu-latest - clang	2m 43s
Build sources on amd64 for windows-latest	10s
Build with various code analysis tools (valgrind)	19s
Build sources on amd64 for macos-latest - gcc	29s
Build sources on amd64 for macos-latest - clang	16s
Build sources on amd64 for windows-2019	1m 30s
	16m 13s

Provide feedback