*) why is the scope selector of the build and other commands source.actionscript.3 , while in the language file the scope is source.actionscript3. When trying to build, the shortcut won't work. With scope selector source.actionscript3 it does. herewith a delta file .
Everything in the bundle was changed to "source.actionscript.3" this allows commands to work with both versions of AS by just targeting source.actionscript
The delta files you have there use source.actionscript3 so you'll need to add the . between there once you have updated your AS3 bundle to the one with the new "source.actionscript.3" scopes.
*) that when you checkout the actionscript 3 bundle you get the following error
http://macromates.com/textmate/manual/bundles#setting_lc_ctype