Add a new disassembler that improves over the previous disassembler

Add a new disassembler that improves over the previous disassembler
in that it provides an abstract (intermediate) representation for
instructions. This significantly improves working with instructions
such as emulation of instructions that are not implemented by the
hardware (e.g. long branch) or enhancing implemented instructions
(e.g. handling of misaligned memory accesses). Not to mention that
it's much easier to print instructions.

Functions are included that provide a textual representation for
opcodes, completers and operands.

The disassembler supports all ia64 instructions defined by revision
2.1 of the SDM (Oct 2002).