OrchardZSA backward compatibility using "if"s #232

Job	Run time
Bitrot check	1m 41s
Test on i686-unknown-linux-gnu	14m 19s
Test on i686-unknown-linux-gnu with beta features	13m 43s
Test on i686-unknown-linux-gnu with nightly features	15m 49s
Book tests	2m 13s
Build target wasm32-unknown-unknown	2m 29s
Build target wasm32-wasi	2m 20s
Intra-doc links	2m 16s
Rustfmt	15s
Test on ubuntu-latest	7m 59s
Test on windows-latest	10m 19s
Test on macOS-latest	8m 56s
Test on ubuntu-latest with beta features	8m 2s
Test on windows-latest with beta features	10m 29s
Test on macOS-latest with beta features	9m 27s
Test on ubuntu-latest with nightly features	8m 57s
Test on windows-latest with nightly features	11m 27s
Test on macOS-latest with nightly features	15m 37s
	2h 26m 18s

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