Fix SDK-14201: Performance: embedded images are written into the swf one byte at a time.
This changes the way swfs are written out when they contain embedded lossless images,
such as PNGs and GIFs. The old code had a loop to write a byte at a time; the new code
does a single biblt. The result is a modest compilation speedup, on the order of
several hundred milliseconds when compiling Flexstore.
(This already went into the trunk as revision 658.)