d: Fix ICE in in force_decl_die, at dwarf2out.c with -gdwarf-2 -gstrict-dwarf [PR98067]

Manifest constants in D are represented as CONST_DECLs, which can be
imported from one module to another.  However, when compiling on strict
dwarf2 targets such as *-*-darwin10, importing CONST_DECLs cannot be
represented in debug as D did not exist as an AT_language until dwarf3,
and the only available fallback being DW_LANG_C.  As CONST_DECLs are
treated as enumerators in C, and not outputted individually in
gen_decl_die, this causes an internal error in force_decl_die to occur.

To handle this, similar to other places in dwarf2out, if a CONST_DECL is
seen in dwarf2out_imported_module_or_decl_1, then we simply return early
if the language is not one of Ada, D, or Fortran.

gcc/ChangeLog:

	PR d/98067
	* dwarf2out.c (dwarf2out_imported_module_or_decl_1): Handle
	  CONST_DECL only if is_fortran, is_ada, or is_dlang.

gcc/testsuite/ChangeLog:

	PR d/98067
	* gdc.dg/debug/debug.exp: New test.
	* gdc.dg/debug/dwarf2/dwarf2.exp: New test.
	* gdc.dg/debug/dwarf2/imports/pr98067.d: New test.
	* gdc.dg/debug/dwarf2/langdw2.d: New test.
	* gdc.dg/debug/dwarf2/langdw3.d: New test.
	* gdc.dg/debug/dwarf2/pr98067.d: New test.
	* gdc.dg/debug/trivial.d: New test.