asjsc warns about missing classes that appear in lib.d.ts but not in externs

[joshtynjala]

[joshtynjala]

The results of dts2as 0.7 no longer result in a compiler error because this version now builds the lib.d.ts into a SWC before compiling the outSWC. However, Google Closure compiler now displays a warning for missing classes. Changed name of this issue to reflect the new situation, but I have no plans to fix anything since it doesn't seem to break. The externs in Apache FlexJS should eventually be updated.