Update stable library feature list by Travis CI build 1548

Author: Travis CI

stable_library_feature.txt

@@ -595,6 +595,7 @@ future_readiness_fns              1.48.0  2020-09-15 23:12:08 +0200  2020-09-15
 raw_fd_reflexive_traits           1.48.0  2020-09-20 13:21:42 +0200  2020-09-20 13:21:42 +0200
 write_mt                          1.48.0  2020-09-21 08:12:40 +0100  2020-09-21 08:12:40 +0100
 slice_ptr_range                   1.48.0  2020-09-23 17:02:58 +0200  2020-09-23 17:02:58 +0200
+renamed_spin_loop                 1.49.0  2020-08-30 10:35:50 +0800  2020-08-30 10:35:50 +0800
 slice_select_nth_unstable         1.49.0  2020-10-06 21:54:05 -0400  2020-10-06 21:54:05 -0400
 nzint_try_from_nzint_conv         1.49.0  2020-10-15 21:30:28 +0200  2020-10-15 21:30:28 +0200
 a                                 b       2019-11-12 11:45:21 +0100  2019-11-12 11:45:21 +0100