Online link to the LEGO NXT firmware (v1.31) source code or IAR ARM LEGO development tools?
What you are asking for doesn't exist at this time.  The links you provide to github are not official LEGO products, but the work of an open source project as described on their home page that has chosen to correspond to the versions released by LEGO itself:


  This is NXT Improved Firmware, an open source community driven work based on
  the original LEGO Mindstorms NXT firmware.
  
  Online resources are accessible on the NXT Improved Firmware web page,
  including documentation, building guides, and more:
  
  http://nxt-firmware.ni.fr.eu.org/
  
  NXT Improved Firmware combines code covered by the LEGO Open Source License
  with code covered by various other open source licenses.  Any file not covered
  by the LEGO Open Source License includes a notice in its header.  All other
  source files are covered by the LEGO Open Source License.  Please see the
  enclosed "LEGO Open Source License" file for more precision on this license
  conditions.


You could file an issue on github and request that they update their project to track the upstream release, but there's no reason to assume they currently have the time and resources to do so.  You could offer to help, or look into what it would take to make the update you're asking for yourself.  Some github projects appreciate new contributions more than others, so I'd definitely open an issue to discuss it before doing a pull request or coding much myself.