[XML,XMLList] Implement normalize() partially

TODO: XML::normalize() should merge adjacent text nodes
Implement valueOf() for numeric types
[Number] Default value in the constructor is 0

Fixes Tamarin Number::valueOf test cases.
[tags] Add support for DefineButton tag
[ImageDecoder] Ensure valid width and height if decodeJPEGImpl fails
[SHAPERECORD] StateNewStyles is used only by DefineShape2/3/4
[DefineFont3] It seems legal to have 1 byte shape records

An example case is
https://www.box.com/representation/f_1999433150/swf/1.swf

Also check that the location of CodeTable matches CodeTableOffset.