alpha return address patch

[Jeffrey A Law]

  In message < 199709152322.QAA14322@cygnus.com >you write:
  > 	This properly implements REUTRN_ADDR_RTX.  It does it in a way
  > 	I don't like -- via elimination to the stack -- to coddle to the
  > 	needs of the current -fno-sjlj-exceptions code.
  > 
  > There is a minor problem with this patch.  You are setting a global
  > variable alpha_function_save_ra during rtl generation, using it after
  > optimization, and then clearing it at the end of output_epilog.  This
  > assumes that these 3 things always occur in sequence.  This is not true.
Jim is absolutely right.  This kind of stuff has bitten the rs6000 and
the PA ports badly over the years it should be avoided since you'll only end
up going back to fix it later.

Jeff