tracing-core 0.1.31

This release of tracing-core fixes a bug that caused threads which call
dispatcher::get_default before a global default subscriber is set to never
see the global default once it is set. In addition, it includes improvements for
instrumentation performance in some cases, especially when using a global
default dispatcher.

Fixed

• Fixed incorrect thread-local caching of Dispatch::none if
  dispatcher::get_default is called before dispatcher::set_global_default
  (#2593)

Changed

• Cloning a Dispatch that points at a global default subscriber no longer
  requires an Arc reference count increment, improving performance
  substantially (#2593)
• dispatcher::get_default no longer attempts to access a thread local if the
  scoped dispatcher is not in use, improving performance when the default
  dispatcher is global (#2593)
• Added #[inline] annotations called by the event! and span! macros to
  reduce the size of macro-generated code and improve recording performance
  (#2555)

Thanks to new contributor @ldm0 for contributing to this release!