add YED geometry convertation + separate cyb string module

cyb_string.h

@@ -0,0 +1,44 @@
+/* -----------------------------------------------------------------------------
+ * The Cyberiada GraphML library implemention
+ *
+ * The string utilities
+ *
+ * Copyright (C) 2024 Alexey Fedoseev <aleksey@fedoseev.net>
+ *
+ * This program 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 3 of the License, or (at your option) any later version.
+ * 
+ * This program 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 General Public License
+ * along with this program. If not, see https://www.gnu.org/licenses/
+ *
+ * ----------------------------------------------------------------------------- */
+
+#ifndef __CYBERIADA_STRING_H
+#define __CYBERIADA_STRING_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* -----------------------------------------------------------------------------
+ * The Cyberiada GraphML string utilities
+ * ----------------------------------------------------------------------------- */
+
+#define MAX_STR_LEN							     4096
+	
+	int cyberiada_copy_string(char** target, size_t* size, const char* source);
+	int cyberiada_string_is_empty(const char* s);
+	int cyberiada_string_trim(char* orig);
+	
+#ifdef __cplusplus
+}
+#endif
+    
+#endif