Readline multiline completer #1544

Job	Run time
Build slim tarball	1m 30s
aarch64-darwin: with shared libraries	29m 43s
x86_64-linux: with shared libraries	30m 57s
aarch64-linux: with shared libraries	25m 22s
x86_64-darwin: with shared libraries	1h 4m 0s
	2h 31m 32s

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