Fix ICE in set_cell_span, at text-art/table.cc:148 with D front-end and -fanalyzer

Fix ICE in set_cell_span, at text-art/table.cc:148 with D front-end and -fanalyzer

The internal error in analyzer turned out to be caused by a subtly
invalid tree representation of STRING_CSTs in the D front-end, fixed by
including the terminating NULL as part of the TREE_STRING_POINTER.

When adding a first analyzer test for D, it flagged up another subtle
mismatch in one assignment in the module support routines as well, fixed
by generating the correct field type for the compiler-generated struct.

	PR d/111537

gcc/d/ChangeLog:

	* expr.cc (ExprVisitor::visit (StringExp *)): Include null terminator
	in STRING_CST string.
	* modules.cc (get_compiler_dso_type): Generate ModuleInfo** type for
	the minfo fields.

gcc/testsuite/ChangeLog:

	* gdc.dg/analyzer/analyzer.exp: New test.
	* gdc.dg/analyzer/pr111537.d: New test.