Added a workaround for compiler failure EXP3231 with --verify.

[reviewed by Sung and Tom]

The test I looked at is test/distributions/dm/t5a.chpl with --no-local;
there are plenty others hitting this even with --local.

This issue (see below) does not seem to affect correctness of the
generated code. I ran through valgrind the t5a executable compiled
with comm=gasnet and --no-verify and it showed no errors.

Details: the failure is due to ref-vs-val type mismatch in expr.cpp:3231,
like this:

(6288145 CallExpr
  (6288146 SymExpr 'fn chpl__autoCopy[5755277]:atomic_int64[27335]')
  (6288147 SymExpr 'ret[6288112]:atomic_int64[27335]'))

vs.

'fn chpl__autoCopy[5755277]:atomic_int64[27335]'
  (5755280 DefExpr 'arg x[5755279]:_ref(atomic_int64)[464345]')
  ...

Once that is resolved, this change needs to be backed out.


git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@21936 3a8e244f-b0f2-452b-bcba-4c88e055c3ca