unix: update openbsd/{386,amd64,arm,arm64,mips64} to OpenBSD 7.1

This closes #115 by updating all relevant files to the 7.1 release

The URL in mkall.sh reflects the 7.1 specific version and will/should
be updated for future versions

unix/mkall.sh

@@ -145,14 +145,14 @@ openbsd_386)
 	mkerrors="$mkerrors -m32"
 	mksyscall="go run mksyscall.go -l32 -openbsd"
 	mksysctl="go run mksysctl_openbsd.go"
-	mksysnum="go run mksysnum.go 'https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/kern/syscalls.master'"
+	mksysnum="go run mksysnum.go 'https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/kern/syscalls.master?rev=1.223&content-type=text/plain'"
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
 	;;
 openbsd_amd64)
 	mkerrors="$mkerrors -m64"
 	mksyscall="go run mksyscall.go -openbsd"
 	mksysctl="go run mksysctl_openbsd.go"
-	mksysnum="go run mksysnum.go 'https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/kern/syscalls.master'"
+	mksysnum="go run mksysnum.go 'https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/kern/syscalls.master?rev=1.223&content-type=text/plain'"
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
 	;;
 openbsd_arm)
@@ -168,7 +168,7 @@ openbsd_arm64)
 	mkerrors="$mkerrors -m64"
 	mksyscall="go run mksyscall.go -openbsd"
 	mksysctl="go run mksysctl_openbsd.go"
-	mksysnum="go run mksysnum.go 'https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/kern/syscalls.master'"
+	mksysnum="go run mksysnum.go 'https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/kern/syscalls.master?rev=1.223&content-type=text/plain'"
 	# Let the type of C char be signed for making the bare syscall
 	# API consistent across platforms.
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs -- -fsigned-char"