next round of removing support for unused systems

[Dan Nicolaescu]

There's still a good amount of dead wood in the tree. 

Stefan asked that the removal be handled like this: 
- the configure script will print an error for emacs-22.2 and ask the
user to email us if they still have a use of the system
- a bit after the 22.2 release remove the support from CVS HEAD>

Systems to desupport:

hp9000s300
m68k HPUX machines 


ibm370aix
The modern IBM mainframes are S390, and don't run AIX.

SVR4 based SINIX-Mips 5.4. 

ncr386

Next

DEC MIPS machines

All AIX before 4.3 

BSD4.x 

BSDI*

HPUX all versions before 11.

Solaris all versions before 2.5 

Ultrix4-3.h

sysv all versions before sysv4