add test for backward compatibility #252

Job	Run time
Build target wasm32-unknown-unknown	1m 40s
Test on i686-unknown-linux-gnu	12m 47s
Build target wasm32-wasi	1m 20s
Test on ubuntu-latest	7m 15s
Test on i686-unknown-linux-gnu with beta features	13m 1s
Test on windows-latest	9m 47s
Test on macOS-latest	6m 28s
Test on i686-unknown-linux-gnu with nightly features	14m 49s
Bitrot check	1m 37s
Test on ubuntu-latest with beta features	7m 2s
Book tests	1m 12s
Test on windows-latest with beta features	10m 14s
Test on macOS-latest with beta features	6m 45s
Intra-doc links	1m 15s
Rustfmt	16s
Test on ubuntu-latest with nightly features	8m 1s
Test on windows-latest with nightly features	11m 24s
Test on macOS-latest with nightly features	15m 7s
	2h 10m 0s

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