strnlen.c: New file.

* strnlen.c: New file.
	* configure.ac: Check for strnlen, add it to AC_LIBOBJ if it's not
	present.
	* Makefile.in: Rebuild dependencies.
	(CFILES): Add strnlen.c.
	(CONFIGURED_OFILES): Add ./strnlen.$(objext).
	* configure, config.in, functions.texi: Rebuild.

	* maint-tool: Accept .def files in the include directory.

From-SVN: r191432

libiberty/strnlen.c

@@ -0,0 +1,30 @@
+/* Portable version of strnlen.
+   This function is in the public domain.  */
+
+/*
+
+@deftypefn Supplemental size_t strnlen (const char *@var{s}, size_t @var{maxlen})
+
+Returns the length of @var{s}, as with @code{strlen}, but never looks
+past the first @var{maxlen} characters in the string.  If there is no
+'\0' character in the first @var{maxlen} characters, returns
+@var{maxlen}.
+
+@end deftypefn
+
+*/
+
+#include "config.h"
+
+#include <stddef.h>
+
+size_t
+strnlen (const char *s, size_t maxlen)
+{
+  size_t i;
+
+  for (i = 0; i < maxlen; ++i)
+    if (s[i] == '\0')
+      break;
+  return i;
+}