d: Merge upstream dmd 313d28b3d, druntime e361d200.

D front-end changes:

    - Import latest bug fixes from the 2.100 release branch.
    - Fix signatures of extern C++ functions that have size_t
      parameters.

gcc/d/ChangeLog:

	* dmd/MERGE: Merge upstream dmd 313d28b3d.
	* d-port.cc (Port::memicmp): Use d_size_t instead of size_t.
	(Port::valcpy): Likewise.

libphobos/ChangeLog:

	* libdruntime/MERGE: Merge upstream druntime e361d200.