bounds checking and traps

[Jan Beulich]

>These are standard named patterns.  Grep for "gen_trap", and note where

>it is called.

I did exactly that, and didn't find any meaningful references (as I
said before, folloiwng the call tree, TRAP_IF must be found somewhere in
order for gen_trap [or gen_conditional_trap] to be called, but I wasn't
able to find anything anywhere that would actually set TRAP_IF).

>Yes, this may need to be OS dependent.

But then this can't be OS-independent (i386.md) code.

Jan