d: Merge upstream dmd a53934d18, phobos 604534d7c.

d: Merge upstream dmd a53934d18, phobos 604534d7c.

D front-end changes:

    - Import dmd v2.100.0.

Phobos changes:

    - Import phobos v2.100.0.

gcc/d/ChangeLog:

	* dmd/MERGE: Merge upstream dmd a53934d18.
	* dmd/VERSION: Update version to v2.100.0.
	* d-codegen.cc (d_decl_context): Use resolvedLinkage to get
	declaration linkage.
	(build_struct_literal): Track offset in bits.
	* d-gimplify.cc (d_gimplify_modify_expr): Check both operands for a
	bit-field reference.
	* d-lang.cc (d_post_options): Set flag_rtti and flag_exceptions if
	-fno-druntime was seen on command-line.
	(d_type_promotes_to): Use resolvedLinkage to get declaration linkage.
	* decl.cc (make_thunk): Likewise.
	* types.cc (layout_aggregate_members): Ignore anonymous fields in
	total count.

libphobos/ChangeLog:

	* src/MERGE: Merge upstream phobos 604534d7c.