Tag failing specs for not not implemented StringScanner methods

Author: andrykonchin

spec/tags/truffle/methods_tags.txt

@@ -102,3 +102,6 @@ fails:Public methods on Method should include dup
 fails:Public methods on String should include dup
 fails:Public methods on UnboundMethod should include dup
 fails:Public methods on StringIO should include pread
+fails:Public methods on StringScanner should include peek_byte
+fails:Public methods on StringScanner should include scan_byte
+fails:Public methods on StringScanner should include scan_integer