Update avr-gcc 4.7.3 to 4.8.3
- libiberty.a will be installed as
    lib/gcc/avr/${PKGVERSION}/libiberty.a
  (previous 4.5.3, and 4.7.3 did not have the one).
  and it is moved from lib/libiberty.a to above to avoid confilct to
  other cross and native tools.

From grepping 'avr' from NEWS file:
---------------------------------
   On AVR, the configure option --with-avrlibc supported since GCC 4.7.2
   is turned on per default for all non-RTEMS configurations. This option
   arranges for a better integration of [3]AVR Libc with avr-gcc. For
   technical details, see [4]PR54461. To turn off the option in non-RTEMS
   configurations, use --with-avrlibc=no. If the compiler is configured
   for RTEMS, the option is always turned off.

     * Support has been added for the AVR-specific configure option
       --with-avrlibc=yes in order to arrange for better integration of
       [3]AVR-Libc. This configure option is supported in avr-gcc 4.7.2
       and newer and will only take effect in non-RTEMS configurations. If
       avr-gcc is configured for RTEMS, the option will be ignored which
       is the same as specifying --with-avrlibc=no. See [4]PR54461 for
       more technical details.

   3. http://www.nongnu.org/avr-libc/
   4. http://gcc.gnu.org/PR54461

#include <avr/io.h> /* Port Definitions from AVR-LibC */

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