Remove crate:: prefixes from crate paths

This is somewhat misleading, as those are actually external crates,
and don't need a crate:: prefix.

clippy_lints/src/empty_enum.rs

@@ -9,10 +9,10 @@
 
 //! lint when there is an enum with no variants
 
-use crate::rustc::hir::*;
-use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use crate::rustc::{declare_tool_lint, lint_array};
 use crate::utils::span_lint_and_then;
+use rustc::hir::*;
+use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
+use rustc::{declare_tool_lint, lint_array};
 
 /// **What it does:** Checks for `enum`s with no variants.
 ///