Fixed a bug in parsing ActionPush with multiple string literals.

[Issue]
  Wrong text is observed.

[Cause]
  There is an ActionPush(type=string) that contains multiple null-terminated string literals.
  In such the case, QuickSWF stops parsing on the first null and moves on to the next action.
  Therefore, if the remaining strings contains Shift-JIS, it is not converted to Unicode and causes wrong glyphs.

[Fix]
  Fixed QuickSWF to parse every string literals.