Add --uniprocessor option to dex-preopt.

This tells the preoptimizer to target a uniprocessor (unsurprisingly).
By default, it targets SMP, which makes it do more changes than it has
to for a uniprocessor (e.g. editing how non-wide volatile fields are
accessed within bytecode). To be clear, when SMP-optimized code is run
on a uniprocessor, it should still work. We're just aiming to only
make truly necessary changes during optimization.

While I was in the territory, I went ahead and cleaned up some single
vs. double quote hygiene in the file.

Change-Id: Ia45992939a436d0be6db8363c43d430de4acb80b