bpo-36878: Track extra text added to 'type: ignore' in the AST (GH-13479)

GH-13238 made extra text after a # type: ignore accepted by the parser.
This finishes the job and actually plumbs the extra text through the
parser and makes it available in the AST.
diff --git a/Python/ast.c b/Python/ast.c
index abc8d89..6259827 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -830,7 +830,10 @@
                 goto out;
 
             for (i = 0; i < num; i++) {
-                type_ignore_ty ti = TypeIgnore(LINENO(CHILD(ch, i)), arena);
+                string type_comment = new_type_comment(STR(CHILD(ch, i)), &c);
+                if (!type_comment)
+                    goto out;
+                type_ignore_ty ti = TypeIgnore(LINENO(CHILD(ch, i)), type_comment, arena);
                 if (!ti)
                    goto out;
                asdl_seq_SET(type_ignores, i, ti);