[0.2] Specify `rust-version = "1.19"` in Cargo.toml #5583

Job	Run time
Docker Linux Tier1 (i686-unknown-linux-gnu)	3m 36s
macOS (x86_64-apple-darwin)	2m 32s
Style check	16s
Windows (x86_64-pc-windows-gnu, 64, x86_64)	4m 23s
Docker Linux Tier1 (x86_64-unknown-linux-gnu)	3m 22s
Windows (x86_64-pc-windows-msvc)	1m 36s
Windows (i686-pc-windows-msvc)	4m 20s
	20m 5s

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