[XML] Work around a bug in libxml++ < 2.35.3

The bug was causing segfaults when text nodes were concatenated in
appendChild()
[XMLBase] Handle comment, PI and CData nodes in buildCopy()
[XMLList] Handle XML declaration in the constructor
[opcodes] Handle also other classes than SyntheticFunction in constructFunction
[Array] Fix an overflow in the setter

0xFFFFFFFF is not a valid index and will be ignored.
[tests] Disable a test case that tries to allocates all memory

until memory limits are implemented
[ASString] Improve toNumber

Whitespace characters from the ECMA specs, UTF-8, parse -Infinity
correctly.
[Error] toString improvements
[tests] Correct dependency ordering of support classes + refactoring

Some Tamarin tests were failing because of wrong ordering of support
.abc files when creating the .swf.
[Number] Fix rounding in toFixed

Was broken since a4eae370