Merge pull request #1468 from tschneidereit/nat

Parallelize `grunt shu` build target
Merge pull request #1469 from tschneidereit/nat

Make IAdvancable instances add themselves to DisplayObject._advancableInstances instead of doing it in the DisplayObject initializer
Check for zero or negative width/height arguments to bitmap data and throw appropriate errors.

There's a bug in Mining truck ATM where shapes are cached in zero by zero bitmap data objects because of bounds issues. This argument test exposes the bug early.
Forgot to write the number of children if the bitmap data is null.
Propagate Fill and Line bounds independently.
Fix font size calculation for static text
Don't use ArgumentError error.
Fix font size issue when the font is exactly 8pt (or 160twips).
Merge pull request #1470 from mbebenita/nat

Check for zero or negative width/height arguments to bitmap data and thr...
Merge branch 'nat' of github.com:mozilla/shumway into nat
Set mouseOver/mouseDown properties and advance button states
Support button mode
Type fix
Revert previous font resolution fix, restore @mbx's version
Add missing semicolons when escaping static text
Merge pull request #1473 from tobytailor/nat

Misc
Change `grunt avm1` and `grunt flash` to also build the relevant .abc files

... in parallel. If the `.as` files didn't change, then this doesn't take any time at all, and if they did, not building the `.abc` files is wrong.

Also removed the `playerglobal` and `avm1lib` aliases, as they're now subsumed in `flash` and `avm1`, respectively.