Set DTR by default when opening a serial port #533

Job	Run time
cargo-deny (advisories)	20s
lint	37s
cargo-deny (bans licenses sources)	29s
aarch64-apple-darwin / build	55s
aarch64-apple-darwin-nightly / build	1m 7s
aarch64-apple-ios / build	1m 30s
aarch64-unknown-linux-gnu / build	44s
aarch64-unknown-linux-musl / build	1m 4s
arm-linux-androideabi / build	31s
armv7-linux-androideabi / build	33s
i686-pc-windows-gnu / build	1m 43s
i686-pc-windows-msvc / build	1m 58s
i686-unknown-linux-gnu / build	34s
i686-unknown-linux-musl / build	1m 4s
msrv-aarch64-apple-darwin / build	1m 42s
msrv-arm-linux-androideabi / build	1m 47s
msrv-x86_64-pc-windows-msvc / build	2m 5s
msrv-x86_64-unknown-freebsd / build	1m 49s
msrv-x86_64-unknown-linux-gnu / build	1m 45s
msrv-x86_64-unknown-linux-musl / build	2m 56s
msrv-x86_64-unknown-netbsd / build	1m 45s
x86_64-apple-darwin / build	1m 8s
x86_64-pc-windows-gnu / build	2m 4s
x86_64-pc-windows-msvc / build	1m 58s
x86_64-pc-windows-msvc-nightly / build	2m 3s
x86_64-unknown-freebsd / build	33s
x86_64-unknown-linux-gnu / build	1m 0s
x86_64-unknown-linux-gnu-nightly / build	1m 11s
x86_64-unknown-linux-musl / build	1m 4s
x86_64-unknown-netbsd / build	33s
	38m 32s

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