(bcopy, bzero, bcmp): Don't undef.

src/s/irix6-0.h

@@ -31,19 +31,4 @@
 #undef ospeed
 #endif
 
-/* Cancel some #define's in usg5-4.h.
-   Larry Hunter <hunter@nlm.nih.gov> said this was needed
-   for Irix 6.5.  Let's see if it is safe in 6.N, N<5, as well.  */
-/* Extrapolating from Irix 6.5, the problem is that (at least) the
-   bzero definition breaks what the X headers do.  The following means
-   that we lack prototypes for these functions, and we presumably lose
-   at least in the 64-bit ABI (though that's only supported on Irix
-   6.5, which I can test).  We may be saved by the fact that these
-   appear to be intrinsics in the SGI (Cray) compiler.  It's probably
-   appropriate to include strings.h here, but I can't test it.  See
-   irix6-5.h.  -- fx  */
-#undef bcopy
-#undef bcmp
-#undef bzero
-
 #undef TIOCSIGSEND