MapTableToParameters: document metadata stowing. #876

Job	Run time
static_checks_debian_stable_x86_64	17s
build_cross_mxe_x86_64	20m 39s
build_debian_buster_aarch64	2h 44m 58s
build_debian_buster_x86_64	12m 20s
build_static_alpine_aarch64	2h 9m 25s
build_static_alpine_armv7	1h 57m 5s
build_static_alpine_x86_64	13m 22s
build_debian_buster_armhf	2h 50m 13s
	10h 28m 19s

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