Add "strict mode" #1764

Job	Run time
Lint	14s
Docs	18s
Test	39s
cargo-deny (aarch64-apple-ios)	18s
Test (json)	47s
cargo-deny (aarch64-linux-android)	18s
Test (charset)	35s
cargo-deny (i686-pc-windows-gnu)	17s
Test (cookies)	39s
cargo-deny (i686-pc-windows-msvc)	19s
Test (socks-proxy)	38s
cargo-deny (i686-unknown-linux-gnu)	18s
Test (native-certs)	45s
cargo-deny (wasm32-unknown-unknown)	18s
Test (gzip)	45s
cargo-deny (x86_64-apple-darwin)	18s
Test (brotli)	36s
cargo-deny (x86_64-apple-ios)	19s
Test (http-crate)	38s
cargo-deny (x86_64-pc-windows-gnu)	21s
Test (http-interop)	37s
cargo-deny (x86_64-pc-windows-msvc)	19s
Test (http-crate http-interop)	37s
cargo-deny (x86_64-unknown-linux-gnu)	18s
Test (tls)	7s
cargo-deny (x86_64-unknown-redox)	18s
Test (tls, json)	1s
Test (tls, charset)	2s
Test (tls, cookies)	2s
Test (tls, socks-proxy)	1s
Test (tls, native-certs)	1s
Test (tls, gzip)	2s
Test (tls, brotli)	7s
Test (tls, http-crate)	2s
Test (tls, http-interop)	1s
Test (tls, http-crate http-interop)	1s
Test (native-tls)	40s
Test (native-tls, json)	4s
Test (native-tls, charset)	43s
Test (native-tls, cookies)	46s
Test (native-tls, socks-proxy)	9s
Test (native-tls, native-certs)	39s
Test (native-tls, gzip)	45s
Test (native-tls, brotli)	42s
Test (native-tls, http-crate)	46s
Test (native-tls, http-interop)	41s
Test (native-tls, http-crate http-interop)	43s
	18m 34s

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