Improve the performance of the generated Erlang code

[chrrasmussen]

The generated Erlang code is not optimal in terms of performance. As a comparison:

• Running the Idris 2 compiler on Erlang and compiling the Idris 2 codebase takes about 20 minutes.
• Running the Idris 2 compiler on Chez Scheme and compiling the Idris 2 codebase takes about 1 minute.

I suspect that Chez Scheme gets a lot of help by the JIT. It is therefore exciting that JIT is in the works for Erlang as well. I still think it is possible to improve the performance, even for non-JIT-ed Erlang.

Somewhat related, the Idris 2 compiler is implemented using the IORef, IOArray, Buffer primitives mentioned in #4. If they can be improved, that might also help on the performance.