Add __builtin_complex to construct complex values (C1X CMPLX* macros)

[Jakub Jelinek]

On Fri, Aug 19, 2011 at 03:55:12PM +0000, Joseph S. Myers wrote:
> Bootstrapped with no regressions on x86_64-unknown-linux-gnu.  Applied
> to mainline.

The new tests ICE on i686-linux:
FAIL: gcc.dg/builtin-complex-err-1.c (internal compiler error)
FAIL: gcc.dg/builtin-complex-err-2.c (internal compiler error)
FAIL: gcc.dg/torture/builtin-complex-1.c  -O*  (internal compiler error)

All the ICEs are on
    case EXCESS_PRECISION_EXPR:
      /* Each case where an operand with excess precision may be
         encountered must remove the EXCESS_PRECISION_EXPR around
         inner operands and possibly put one around the whole
         expression or possibly convert to the semantic type (which
         c_fully_fold does); we cannot tell at this stage which is
         appropriate in any particular case.  */
      gcc_unreachable ();
in c_fully_fold_internal.

	Jakub