Support reverse lookup of bit offset about pal

[JaredWright]

If we go down the path of generating a function that returns a field's name given the field's bit position, I foresee the following complexities:

• Some fields are 1 bit, some fields are a range of bits
• Registers have a name (sort of a like a weak "id") and a long name (a more human-readable version, if defined)
• Some registers have more than one fieldset. In other words, you must decide how to interpret the register's contents based on external factors (e.g. this CPUID leaf)

This sounds possible, but I'm wondering if there is another more general approach to tackle the immediate problem you face: printing a human-friendly message when a semantic constraint is violated about a CPU's usage. What do you think about the idea outlined in Discussion #82?