The node description system should be reworked further

[DeVaukz]

Some problems with the current implementation:

• It is difficult to (re)construct the C structure layout for a node. This is needed when implementing a disassembler, where you want to display structures overlaid on top of the raw binary data.

• Node layouts are re-created with each call to -layout. Layouts should be cached. Many layouts are the same for all instances of a node type and could be defined at the class (vs instance) level.

• The current mechanism for describing bitfields is less than ideal.

• The type of an MKNodeField is attempting to describe both the semantic type of the field as well as the data type. These should be split.

• MKNodeFieldOptions should be removed. It was added to simplify the implementation of Mach-O Explorer, with the justification that other viewer apps built with Mach-O Kit could also use it. But its purpose is too narrow. It does not belong in Mach-O Kit.