Begin sandboxing support, README updates.

sandbox/sandbox-openbsd.h

@@ -0,0 +1,15 @@
+#ifndef SANDBOXOPENBSD_H
+#define SANDBOXOPENBSD_H
+#include "sandbox.h"
+
+class SandboxOpenBSD : public Sandbox
+{
+  public:
+	bool supported() override;
+	bool enableForInit() override;
+	bool enableForWorker() override;
+
+  private:
+	bool seccomp_blacklist(std::vector<int> syscalls);
+};
+#endif