valgrind: add suppressions for undefined use

valgrind will warn that OpenSSL will use undefined data in connect/read
when talking to certain other TLS stacks.  Thankfully, this only seems
to occur when gcc is the compiler, so hopefully valgrind is just
misunderstanding an optimization.  Regardless, suppress this warning.

script/valgrind.supp

@@ -124,6 +124,26 @@
 }
 
 {
+	ignore-openssl-undefined-in-read
+	Memcheck:Cond
+	...
+	obj:*libssl.so*
+	...
+	fun:openssl_read
+	...
+}
+
+{
+	ignore-openssl-undefined-in-connect
+	Memcheck:Cond
+	...
+	obj:*libssl.so*
+	...
+	fun:openssl_connect
+	...
+}
+
+{
 	ignore-libssh2-rsa-sha1-sign
 	Memcheck:Leak
 	...

src/streams/openssl.c

@@ -597,6 +597,10 @@ static int openssl_connect(git_stream *stream)
 
 	st->connected = true;
 
+#ifdef VALGRIND
+	VALGRIND_MAKE_MEM_DEFINED(st->ssl, sizeof(SSL));
+#endif
+
 	return verify_server_cert(st->ssl, st->host);
 }