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-cplus-types.c

@@ -595,7 +595,7 @@ compile_cplus_convert_struct_or_union_members
       gcc_type field_type
 	= instance->convert_type (TYPE_FIELD_TYPE (type, i));
 
-      if (field_is_static (&TYPE_FIELD (type, i)))
+      if (field_is_static (&type->field (i)))
 	{
 	  CORE_ADDR physaddr;