rustc_llvm: Remove the inner llvm module

This makes it much saner for clients to use the library since
they don't have to worry about shadowing one llvm with another.
diff --git a/src/librustc/middle/trans/cabi.rs b/src/librustc/middle/trans/cabi.rs
index df1347f..0a10fb8 100644
--- a/src/librustc/middle/trans/cabi.rs
+++ b/src/librustc/middle/trans/cabi.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use lib::llvm::Attribute;
+use llvm::Attribute;
 use std::option;
 use middle::trans::context::CrateContext;
 use middle::trans::cabi_x86;