PATCH: add pa2.0 system instructions

[Jeffrey A Law]

  In message < 14213.64155.863403.101617@gargle.gargle.HOWL >you write:
  > This looks similar to mine, except I used 'l' and 'L' for long offsets, and
  > 'm' for the completer.  Also I didn't have a strict syntax flag.
In mine, I'd used 'l' and 'L' for the FP loads/stores.  Note the integer and
FP long displacement loads & stores have to use different letters.


  > Perhaps I don't understand here, but this doesn't seem ambiguous to me. 
  > There isn't ambiguity in the 0, 4, or 9.  In the old syntax, 5 can only be
  > a displacement.
But the code which parses an 'x' operand (or any register operand) will accept
an immediate and treat it like a register number.  So, if you are using
existing letters to stand for registers, then you've got no way to distinguish
between those cases.  It's a serious issue.

Given the table fragment I posted, there's no way to get load-word with short
displacement without modifying how the 'x' and other register operands are
handled because 'x' will interpret the short displacement as a register #.

jeff