Rename "cranelift-meta" to just "meta".

This makes it easier for the publish-all.sh script to know to skip this
crate, and it avoids the need to use `extern cranelift_meta as meta`.

lib/codegen/build.rs

@@ -18,7 +18,7 @@
 // The build script expects to be run from the directory where this build.rs file lives. The
 // current directory is used to find the sources.
 
-extern crate cranelift_meta as meta;
+extern crate meta;
 
 use std::env;
 use std::process;