[i386] pni => sse3 -- GCC 3.3.3 related

[Kelley Cook]

The 90nm version of the Pentium 4 (formerly code named Prescott) was 
released yesterday.  Somewhat surprisingly, the chip was not given a new 
name.

Unsurprisingly, PNI (Prescott New Instructions) were renamed to SSE3. 
This mechanical patch updates GCC accordingly.

Note that this renaming is riding on the fact that "-mpni" support has 
not yet been included in a FSF released compiler.  However, this feature 
was backported to be included in GCC 3.3.3 
(http://gcc.gnu.org/ml/gcc-cvs/2003-11/msg00096.html).  Personally I 
think it would be a mistake to include an option switch which was based 
on an internal codename in a released compiler -- especially a bug fix 
compiler.  If 3.3.3 is released as is then "-mpni" will have to be 
supported for years afterward.

This is why I believe that either this patch also needs to included with 
GCC 3.3.3 or else the recently added PNI support should be reverted from 
3.3.3.

Patch was bootstrapped on pentium4-pc-cygwin — though I do not have 
Pentium 4 E-step to test its effectiveness on.

OK?
3.4?
3.3.3?