Issue #1580: use short float repr where possible. - incorporate and adapt David Gay's dtoa and strtod into the Python core - on platforms where we can use Gay's code (almost all!), repr(float) is based on the shortest sequence of decimal digits that rounds correctly. - add sys.float_repr_style attribute to indicate whether we're using Gay's code or not - add autoconf magic to detect and enable SSE2 instructions on x86/gcc - slight change to repr and str: repr switches to exponential notation at 1e16 instead of 1e17, str switches at 1e11 instead of 1e12

--- a/Include/Python.h	Thu Apr 16 18:37:24 2009 +0000
+++ b/Include/Python.h	Thu Apr 16 19:52:09 2009 +0000
@@ -118,6 +118,7 @@
 
 #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);