Use $crate and macro reexport to reduce duplicated code

Many of libstd's macros are now re-exported from libcore and libcollections.
Their libstd definitions have moved to a macros_stage0 module and can disappear
after the next snapshot.

Where the two crates had already diverged, I took the libstd versions as
they're generally newer and better-tested. See e.g. d3c831b, which was a fix to
libstd's assert_eq!() that didn't make it into libcore's.

Fixes #16806.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index d646245510d..0cda2e4a9c6 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -130,6 +130,7 @@ mod array;
 #[doc(hidden)]
 mod core {
     pub use panicking;
+    pub use fmt;
 }
 
 #[doc(hidden)]