[Ada] arm-linux port for GCC 4.5

[Eric Botcazou]

I propose that we merge Mickael Pettersson's patch:
  http://gcc.gnu.org/ml/gcc-patches/2009-09/msg00450.html
to have a functional arm-linux port of GNAT in GCC 4.5.

This would yield an Ada compiler with a clean testsuite:
  http://gcc.gnu.org/ml/gcc-testresults/2010-01/msg00419.html

Although it's still an SJLJ port, I don't think we should let the best be the 
enemy of the good here and wait for a hypothetical ZCX port (on which no one 
is working for GCC 4.5 as far as I know).

-- 
Eric Botcazou