fixups for calls to gen_rtx()

[David S. Miller]

   From: Richard Henderson <rth@cygnus.com>
   Date: Mon, 22 Sep 1997 11:20:57 -0700 (PDT)

   I disagree; varargs is slow.  There is no need to be dropping the
   last four register arguments into memory just so we can pull them
   out again.

I honestly don't care how slow it is, I really want the type checking.

The NULL_RTX patch was not fun to make once I noticed that the problem
did exist, walking over all of the calls to gen_rtx in the entire
tree.  I'm sure there are other cases of mis-passing of arguments that
I did not catch, the gen_rtx_*() scheme would allow us to catch them
all before they wreak havoc because the compiler would tell us. ;-)

Later,
David "Sparc" Miller
davem@caip.rutgers.edu