[ping] [ARM] Fix register r3 wrongly used to save ip in nested APCS frame

[Eric Botcazou]

The patch is at:
  http://gcc.gnu.org/ml/gcc-patches/2013-09/msg00308.html
and an Ada testcase at:
  http://gcc.gnu.org/ml/gcc-patches/2013-10/msg00910.html

Thanks in advance.

-- 
Eric Botcazou