message: tests: replace "cfg(test)" with "cfg(doctest)" for readme testing
  rustdoc now passes "doctest" when running in test mode.
  PR
diff: @@ -622,7 +622,7 @@ compile_error!("`std` feature is currently required to build this crate");
  #[cfg(feature = "perf-literal")]
  extern crate aho_corasick;
  -#[cfg(test)]
  +#[cfg(doctest)]
  extern crate doc_comment;
  #[cfg(feature = "perf-literal")]
  extern crate memchr;
  @@ -633,7 +633,7 @@ extern crate regex_syntax as syntax;
  #[cfg(feature = "perf-cache")]
  extern crate thread_local;
  -#[cfg(test)]
  +#[cfg(doctest)]
  doc_comment::doctest!("../README.md");
  #[cfg(feature = "std")]
  