d: Merge upstream dmd 09db0c41e, druntime e68a5ae3.

* New core.math.toPrec templates have been added as an intrinsic.

  Some floating point algorithms, such as Kahan-Babuska-Neumaier
  Summation, require rounding to specific precisions. Rounding to
  precision after every operation, however, loses overall precision in
  the general case and is a runtime performance problem.

  Adding these functions guarantee the rounding at required points in
  the code, and document where in the algorithm the requirement exists.

* Support IBM long double types in core.internal.convert.

* Add missing aliases for 64-bit vectors in core.simd.

* RUNNABLE_PHOBOS_TEST directive has been properly integrated into the
  D2 language testsuite.

Reviewed-on: https://github.com/dlang/druntime/pull/3063
	     https://github.com/dlang/dmd/pull/11054

gcc/d/ChangeLog:

	* intrinsics.cc (expand_intrinsic_toprec): New function.
	(maybe_expand_intrinsic): Handle toPrec intrinsics.
	* intrinsics.def (TOPRECF, TOPREC, TOPRECL): Add toPrec intrinsics.