helper: add base64 encoding/decoding helpers from FreeBSD

These helpers are needed by the updated RISC-V target files.

Change-Id: I5aa9f4e58eb75e1c7a1e8e0e3961725e2a915ebb
Signed-off-by: Bernhard Rosenkränzer <bero@baylibre.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/8895
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

src/helper/base64.h

@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+
+/*
+ * Base64 encoding/decoding (RFC1341)
+ * Copyright (c) 2005, Jouni Malinen <j@w1.fi>
+ *
+ * Original file from FreeBSD code
+ * https://cgit.freebsd.org/src/tree/contrib/wpa/src/utils/base64.h?id=f05cddf940db
+ */
+
+#ifndef BASE64_H
+#define BASE64_H
+
+unsigned char *base64_encode(const unsigned char *src, size_t len,
+			      size_t *out_len);
+unsigned char *base64_decode(const unsigned char *src, size_t len,
+			      size_t *out_len);
+
+#endif /* BASE64_H */