Hello,

I was trying to figure out why I was seeing:

$ gdb
(gdb) maint print register-groups
  Name         Nr  Rel Offset    Size  Type            Groups
  eax           0    0      0       4  int 
general,all,save,restore
...
  mm0          32    0    176       8  _vec64i 
sse,mmx,general,all,vector
  mm1          33    1    184       8  _vec64i 
mmx,general,all,vector
...

when adding i386 specific register groups.  Notice how mm0 ended up in 
the SSE register group :-(  The problem was that tests like 
IS_SSE_REGNUM_P() and more specifically regnum==MXCSR_REGNUM weren't 
sufficient - they can trigger a false positive when the ISA doesn't have 
one set of registersSSE registers (the num can match an mmx register - 
regnum == MXCSR_REGNUM == MM0_REGNUM :-().

The attached:

- converts all the macro's into functions

- makes the function checks more robust - return true when both the 
regnum matches and the ISA has the register

- adds a method to test for the orig_eax register (the 
I386_LINUX_ORIG_EAX_REGNUM is moved from i386-linux-tdep.h to i386-tdep.h).

Ok to commit?

Andrew