[D] Fix regression in py-lookup-type.exp

[D] Fix regression in py-lookup-type.exp

In the console interpreter, primitive types are resolved in the expression
parser.  However that didn't take into consideration the script interface.

gdb/ChangeLog:

	* d-namespace.c (d_lookup_symbol): New arg langdef.
	All callers updated.  Support looking up symbol as a primitive type.
	(lookup_module_scope): New arg langdef.  All callers updated.
	Call d_lookup_symbol directly for simple bare symbols.