Remove panic-implementation

rust-lang/rust#51647 has been fixed, so We can remove this hack

Author: paoloteti

Cargo.toml

@@ -9,9 +9,6 @@ test = false
 [build-dependencies]
 cc = { optional = true, version = "1.0" }
 
-[dev-dependencies]
-panic-implementation = { path = 'crates/panic-implementation' }
-
 [features]
 default = ["compiler-builtins"]
 

appveyor.yml

@@ -15,7 +15,7 @@ environment:
     # so we skip that test for now. Would be great to not skip it!
     - TARGET: i686-pc-windows-gnu
       MINGW_URL: https://s3-us-west-1.amazonaws.com/rust-lang-ci2/rust-ci-mirror
-      MINGW_ARCHIVE: i686-6.3.0-release-win32-dwarf-rt_v5-rev1.7z
+      MINGW_ARCHIVE: i686-6.3.0-release-posix-dwarf-rt_v5-rev2.7z
       MINGW_DIR: mingw32
       DEBUG_LTO_BUILD_DOESNT_WORK: 1
     - TARGET: x86_64-pc-windows-gnu

crates/panic-implementation/Cargo.toml

@@ -11,11 +11,9 @@
 #![feature(lang_items)]
 #![feature(start)]
 #![feature(allocator_api)]
-#![feature(panic_implementation)]
 #![cfg_attr(windows, feature(panic_unwind))]
 #![no_std]
 
-extern crate panic_implementation;
 
 #[cfg(not(thumb))]
 #[link(name = "c")]