Update What's New in Python 3.15

Reformat also the doc to fit into 80 columns.

Author: vstinner

Doc/library/sys.rst

@@ -694,9 +694,10 @@ always available. Unless explicitly noted otherwise, all variables are read-only
    A :term:`named tuple` holding information about the float type. It
    contains low level information about the precision and internal
    representation.  The values correspond to the various floating-point
-   constants defined by C implementation and in the standard header file :file:`float.h` for the 'C'
-   programming language; see Annex F and section 5.2.4.2.2 of the 1999 ISO/IEC C standard
-   [C99]_, 'Characteristics of floating types', for details.
+   constants defined by C implementation and in the standard header file
+   :file:`float.h` for the 'C' programming language; see Annex F and section
+   5.2.4.2.2 of the 1999 ISO/IEC C standard [C99]_, 'Characteristics of
+   floating types', for details.
 
    .. list-table:: Attributes of the :data:`!float_info` :term:`named tuple`
       :header-rows: 1

Doc/whatsnew/3.15.rst

@@ -703,6 +703,11 @@ sys
 * Add :data:`sys.abi_info` namespace to improve access to ABI information.
   (Contributed by Klaus Zimmermann in :gh:`137476`.)
 
+* Add :data:`sys.float_info.iec_60559 <sys.float_info>`: a boolean flag,
+  indicating support the IEC 60559 floating-point standard (as specified by the
+  Annex F of C99).
+  (Contributed by Sergey B Kirpichev in :gh:`138580`.)
+
 
 tarfile
 -------

Misc/NEWS.d/next/Library/2025-09-12-07-30-13.gh-issue-138580.Qr_fSH.rst

@@ -1,2 +1,3 @@
-Add a boolean flag, indicating support the IEC 60559 floating-point standard
-(as specified by the Annex F of C99).  Patch by Sergey B Kirpichev.
+Add :data:`sys.float_info.iec_60559 <sys.float_info>`: a boolean flag,
+indicating support the IEC 60559 floating-point standard (as specified by the
+Annex F of C99).  Patch by Sergey B Kirpichev.