mat4.fromRotationTranslationScaleOrigin slight speedup

[flowtsohg]

Cached local array accesses.

I doubt many people will notice the difference.
My library calls this function possibly millions of times per second, so every bit of speed counts.

[toji]

This change needs to be rebased against master now that #249 has landed, but I'd be happy to merge it at that point, thanks!

[stefnotch]

@flowtsohg Mind updating your pull request? It currently has a bunch of conflicts.

[flowtsohg]

I am not very experienced with Github, does this mean I need to re-fork the repository and re-pull?

[stefnotch]

@flowtsohg You don't need a new fork. You have to pull from the latest master, fix the merge conflicts and then, you would have to commit and push.

Though, it should be easily possible to resolve the merge conflicts right here in the browser: https://help.github.com/articles/resolving-a-merge-conflict-on-github/

[flowtsohg]

I am pretty sure I messed something up, but I guess it worked in the end. :)

[stefnotch]

@toji This change can now be merged.

[stefnotch]

@toji Mind merging this?