Only destroy already constructed display objects.
Merge pull request #579 from tobeytailor/timeline

Only destroy already constructed display objects.
Adds global flash object
Moves avm1 globals initialization
Misc avm1: extending, variable resolution, refact
Implements _constructSymbol; makes AVM1 functions good for AVM2 new
Merge pull request #580 from yurydelendik/avm1-5

Misc AVM1 fixes