boring-sys: include HPKE header file for bindgen #935

Job	Run time
clippy	8m 25s
Cross build from macOS to Linux (x86_64-unknown-linux-gnu)	1m 50s
Cross build from macOS to Linux (FIPS) (x86_64-unknown-linux-gnu)	4m 2s
rustfmt	12s
Test (stable)	3m 50s
Test FIPS integration	3m 16s
Test features	7m 20s
Test (arm-android)	2m 8s
Test (arm64-android)	2m 23s
Test (i686-android)	2m 32s
Test (x86_64-android)	2m 5s
Test (aarch64-ios)	2m 22s
Test (aarch64-ios-sim)	2m 20s
Test (x86_64-ios)	2m 38s
Test (i686-linux)	2m 25s
Test (arm-linux)	2m 24s
Test (aarch64-linux)	2m 34s
Test (arm64-macos)	3m 58s
Test (x86_64-macos)	2m 23s
Test (x86_64-mingw)	5m 0s
Test (i686-msvc)	6m 59s
Test (x86_64-msvc)	5m 14s
	1h 16m 20s

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