Simplify and optimize DisplayObject#_getConcatenatedMatrix

Turns two recursion up the display list into one, removes the need to build up a list of display objects, the iteration over said list, and the creation of a temporary Matrix instance. And is shorter.
Remove default argument values from some internal methods

These are always called with all paramters, so we can save the overhead.
Optimize more Matrix usage in DisplayObject

Gets rid of a few superfluous copying operations of all of a matrix's members, and of a temporary matrix allocation in `_getTransformedBounds`.
Merge pull request #1377 from tschneidereit/nat

Reduce garbage generation in Matrix-using DisplayObject operations