Add support reading D modules from DWARF

Add support reading D modules from DWARF

Extends existing support for namespaces/modules in C++/Fortran/Java to
include language_d too.  However unlike Fortran/C++, the separator for
qualified names is a single dot.

2015-07-14  Iain Buclaw  <ibuclaw@gdcproject.org>

	* dwarf2read.c (find_slot_in_mapped_hash): Extend language support to
	also test for language_d.
	(dwarf2_compute_name): Likewise.
	(read_func_scope): Likewise.
	(read_structure_type): Likewise.
	(determine_prefix): Likewise.
	(read_import_statement): Use dot as the separator for language_d.
	(typename_concat): Likewise, but don't prefix the D main function.