add support for SWC

[zwetan]

it would be nice to be able to manipulate SWC files

• read SWC
• open/extract a file inside a SWC
• obtain the list of embedded definitions
  like classes, functions, etc.
• extract all the ABC files from the
  internal library.swf
• write SWC
• etc.

[zwetan]

we should also investigate if we can compile against a SWC
I think it's possible with ASC2

it would allow scenarios as
compile( "myprogram.abc", [ "somelib.swc" ] );

with maybe the clear advantage to embed only the bytecode used by the program
eg. a big SWC of 100MB, but you use only 1 definition, and so your final program
embed only 10KB of those 100MB