Explicitly number ShapeData commands

For easier debugging.
Use the rudimentary implementation of `isXMLName` in xml.ts as the native of the same name

Currently, this assumes that SpiderMonkey has `isXMLName`. Since the E4X removal, that's not true, anymore.
Move AVM2 ops with contextually reserved keywords as names to the end of the enum

 IntelliJ thinks these are syntax errors, and then can't find any following ops either. Much nicer to have all those ops.
Implement support for EOFError thrown in DataBuffer (and hence ByteArray)

This is complicated by to things:
 - DataBuffer is part of the `base` package and hence can't rely on the `Shumway.AVM2.Errors` object or the `Shumway.AVM2.Runtime.throwError` function. For that, global var declarations are added in `base/references.ts` and filled in in the avm2 package
 - `throwError`, until now, only supported top-level error classes. For that, an `fqn` field has been added to the error definitions in `Shumway.AVM2.Errors`
Merge pull request #1797 from tschneidereit/master

Implement EOFError + changes useful for debugging