Add compat strnlen() implementation for non-GLIBC systems

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

strnlen.h

@@ -0,0 +1,44 @@
+/* strnlen.h - Re-implementation of GLIBC strnlen()
+ *
+ * Copyright (c) 2016  Joachim Nilsson <troglobit@gmail.com>
+ *
+ * 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.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef LITE_STRNLEN_H
+#define LITE_STRNLEN_H
+
+#if !defined(HAVE_STRNLEN)
+#if defined(strnlen)
+#define HAVE_STRNLEN	1
+#endif
+#endif
+
+
+#if !HAVE_STRNLEN
+#include <stddef.h>	/* size_t */
+
+#define strnlen(str, lim) xstrnlen(str, lim)
+
+static inline size_t xstrnlen(const char *str, size_t lim)
+{
+	size_t i = 0;
+
+	while (str[i] && i < lim)
+		i++;
+
+	return i;
+}
+#endif
+
+#endif /* LITE_STRNLEN_H */