Issue #7117: Prepare for backport of py3k float repr.
Add the Python/dtoa.c file containing the main algorithms;
add corresponding include file and include in Python.h;
include license information for Python/dtoa.c;
add dtoa.c and dtoa.h to Makefile.
diff --git a/Doc/license.rst b/Doc/license.rst
index 278bb2d..6e327ea 100644
--- a/Doc/license.rst
+++ b/Doc/license.rst
@@ -708,3 +708,35 @@
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
+
+
+strtod and dtoa
+---------------
+
+The file :file:`Python/dtoa.c`, which supplies C functions dtoa and
+strtod for conversion of C doubles to and from strings, is derived
+from the file of the same name by David M. Gay, currently available
+from http://www.netlib.org/fp/. The original file, as retrieved on
+March 16, 2009, contains the following copyright and licensing
+notice::
+
+ /****************************************************************
+ *
+ * The author of this software is David M. Gay.
+ *
+ * Copyright (c) 1991, 2000, 2001 by Lucent Technologies.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose without fee is hereby granted, provided that this entire notice
+ * is included in all copies of any software which is or includes a copy
+ * or modification of this software and in all copies of the supporting
+ * documentation for such software.
+ *
+ * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
+ * WARRANTY. IN PARTICULAR, NEITHER THE AUTHOR NOR LUCENT MAKES ANY
+ * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
+ * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
+ *
+ ***************************************************************/
+
+