$NetBSD$

Add NetBSD support

--- configure.orig	2023-07-02 04:19:49.706748744 +0000
+++ configure
@@ -57,6 +57,11 @@ case "$(uname)" in
 		config libtls
 		defvar OPENSSL_BIN openssl exec_prefix /bin/openssl
 		;;
+	(NetBSD)
+		cflags "-D'explicit_bzero(b,l)=explicit_memset((b),0,(l))'"
+		config libtls
+		defstr OPENSSL_BIN /usr/bin/openssl
+		;;
 	(*)
 		config libtls
 		defvar OPENSSL_BIN openssl exec_prefix /bin/openssl