Update gcc-avr 4.8.3 to 4.9.1
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http://gcc.gnu.org/gcc-4.9/index.html
                             GCC 4.9 Release Series
   July 16, 2014

   The [1]GNU project and the GCC developers are pleased to announce the
   release of GCC 4.9.1.

   This release is a bug-fix release, containing fixes for regressions in
   GCC 4.9.0 relative to previous releases of GCC.

Release History
   GCC 4.9.1
          July 16, 2014 ([2]changes, [3]documentation)
   GCC 4.9.0
          April 22, 2014 ([4]changes, [5]documentation)

   2. https://gcc.gnu.org/PR60825
   3. https://gcc.gnu.org/gcc-4.9/porting_to.html
   4. http://openmp.org/wp/openmp-specifications/
   5. https://gcc.gnu.org/onlinedocs/gcc-4.9.0/gcc/Optimize-Options.html#index-fsimd-cost-model-908
Remove TODO for the moment.