add fgetline(3) implementation

libifupdown/fgetline.h

@@ -0,0 +1,25 @@
+/*
+ * libifupdown/fgetline.h
+ * Purpose: portable fgetline(3)
+ *
+ * Copyright (c) 2020 Ariadne Conill <ariadne@dereferenced.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * This software is provided 'as is' and without any warranty, express or
+ * implied.  In no event shall the authors be liable for any damages arising
+ * from the use of this software.
+ */
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+
+#ifndef LIBIFUPDOWN_FGETLINE_H__GUARD
+#define LIBIFUPDOWN_FGETLINE_H__GUARD
+
+extern char *lif_fgetline(char *line, size_t size, FILE *stream);
+
+#endif