token, kex: Add functions to handle tokens lists

The added functions allow splitting chains of tokens separated by a
given character (usually ','), and extracting matching parts between two
chains of tokens.

The previously existing functions in kex.c were replaced by the
introduced ones.

Signed-off-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

include/libssh/token.h

@@ -0,0 +1,44 @@
+/*
+ * token.h - Tokens list handling
+ *
+ * This file is part of the SSH Library
+ *
+ * Copyright (c) 2019 by Red Hat, Inc.
+ *
+ * Author: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>
+ *
+ * The SSH Library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or (at your
+ * option) any later version.
+ *
+ * The SSH Library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with the SSH Library; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+#ifndef TOKEN_H_
+#define TOKEN_H_
+
+struct ssh_tokens_st {
+    char *buffer;
+    char **tokens;
+};
+
+struct ssh_tokens_st *ssh_tokenize(const char *chain, char separator);
+
+void ssh_tokens_free(struct ssh_tokens_st *tokens);
+
+char *ssh_find_matching(const char *available_d,
+                        const char *preferred_d);
+
+
+char *ssh_find_all_matching(const char *available_d,
+                            const char *preferred_d);
+#endif /* TOKEN_H_ */