Making the builtins a little neater. Closures weren't very friendly for debuggers/backtrace

Created by: drosseau

There are two changes in here.

1. I noticed unalias was at some point accidentally defined as a drop so we had drop down twice.
2. The closure method made it a little more difficult than it needed to be to see what errored with RUST_BACKTRACE=1 and to set breakpoints in a debugger. Now instead of {{closure}} you'll get the actual function.