Don't have oldtime feature as default for stable releases

As this feature pulls in a dependency on time 0.1 which fail a security
audit, it should not be included as a default feature. The corresponding
Rust advisory can be found here:

https://rustsec.org/advisories/RUSTSEC-2020-0071

Cargo.toml

@@ -17,7 +17,7 @@ rust-version = "1.57.0"
 name = "chrono"
 
 [features]
-default = ["clock", "std", "oldtime", "wasmbind"]
+default = ["clock", "std", "wasmbind"]
 alloc = []
 libc = []
 winapi = ["windows-targets"]

README.md

@@ -61,7 +61,7 @@ Optional features:
 * `serde`: Enable serialization/deserialization via serde.
 * `rkyv`: Enable serialization/deserialization via rkyv.
 * `rustc-serialize`: Enable serialization/deserialization via rustc-serialize (deprecated).
-* `old_time`: compatability with the `Duration` type of the `time` 0.1 crate (deprecated).
+* `oldtime`: compatability with the `Duration` type of the `time` 0.1 crate (deprecated).
 * `arbitrary`: construct arbitrary instances of a type with the Arbitrary crate.
 * `unstable-locales`: Enable localization. This adds various methods with a `_localized` suffix.
   The implementation and API may change or even be removed in a patch release. Feedback welcome.