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/Include/Python.h b/Include/Python.h
index 9e140a5..eac9f48 100644
--- a/Include/Python.h
+++ b/Include/Python.h
@@ -137,6 +137,7 @@
#include "pyctype.h"
#include "pystrtod.h"
#include "pystrcmp.h"
+#include "dtoa.h"
/* _Py_Mangle is defined in compile.c */
PyAPI_FUNC(PyObject*) _Py_Mangle(PyObject *p, PyObject *name);