c++: ICE initializing array of aggrs [PR117985]

This crash started with my r12-7803 but I believe the problem lies
elsewhere.

build_vec_init has cleanup_flags whose purpose is -- if I grok this
correctly -- to avoid destructing an object multiple times.  Let's
say we are initializing an array of A.  Then we might end up in
a scenario similar to initlist-eh1.C:

  try
    {
      call A::A in a loop
      // #0
      try
        {
	  call a fn using the array
	}
      finally
	{
	  // #1
	  call A::~A in a loop
	}
    }
  catch
    {
      // #2
      call A::~A in a loop
    }

cleanup_flags makes us emit a statement like

  D.3048 = 2;

at #0 to disable performing the cleanup at #2, since #1 will take
care of the destruction of the array.

But if we are not emitting the loop because we can use a constant
initializer (and use a single { a, b, ...}), we shouldn't generate
the statement resetting the iterator to its initial value.  Otherwise
we crash in gimplify_var_or_parm_decl because it gets the stray decl
D.3048.

	PR c++/117985

gcc/cp/ChangeLog:

	* init.cc (build_vec_init): Pop CLEANUP_FLAGS if we're not
	generating the loop.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/initlist-array23.C: New test.
	* g++.dg/cpp0x/initlist-array24.C: New test.