register interface

[Andrew Cagney <cagney at redhat dot com>]

Chatted with Adam a bit today about registers.

The big takeaway is to know that the Task interface isn't intended for a 
big fancy fancy register window, and in all probably will be re-factored 
a few more times.   It is intended just for read-only raw register access.

To understand the difference, using gdb compare:

  $ gdb gdb
  (gdb) b main
  (gdb) run
  (gdb) maint print cooked-registers
  .....

which dumps out an internal register representation; and compare it to 
the user command:

  (gdb) info all-registers
  ...

which dumps out registers represented as more fancy objects|types.  For 
insance:

  print $mm7
 $1 = {uint64 = 0x0, v2_int32 = {0x0, 0x0}, v4_int16 = {0x0, 0x0, 0x0, 
0x0},
 v8_int8 = "\000\000\000\000\000\000\000"}

The frysk Task's register interface is very much like the former - 
provide just primitive values - and so the register window would want to 
limit itself to just that.

Otherwise the whole effort will get dragged into the register-window 
feature breading rat-hole :-)

Andrew