Nuke globals.asm

Needs bugfix https://github.com/bentley/rgbds/pull/16 to build.

before:
```
$ make clean
$ time make

real	0m48.921s
user	0m28.618s
sys 	0m4.428s
```

after:
```
$ make clean
$ time make

real	0m20.842s
user	0m15.777s
sys 	0m1.820s
```