gdb: remove TYPE_FIELD macro

Replace all uses of it by type::field.

Note that since type::field returns a reference to the field, some spots
are used to assign the whole field structure.  See ctfread.c, function
attach_fields_to_type, for example.  This is the same as was happening
with the macro, so I don't think it's a problem, but if anybody sees a
really nicer way to do this, now could be a good time to implement it.

gdb/ChangeLog:

	* gdbtypes.h (TYPE_FIELD): Remove.  Replace all uses with
	type::field.

gdb/compile/compile-c-symbols.c

@@ -527,7 +527,7 @@ generate_vla_size (compile_instance *compiler,
 	int i;
 
 	for (i = 0; i < type->num_fields (); ++i)
-	  if (!field_is_static (&TYPE_FIELD (type, i)))
+	  if (!field_is_static (&type->field (i)))
 	    generate_vla_size (compiler, stream, gdbarch, registers_used, pc,
 			       TYPE_FIELD_TYPE (type, i), sym);
       }