Make `as' compile before it is axed. It still uses the archaic BSD

interface setbuffer(), and emulates setbuffer() on USG systems using a
#define of setbuffer() in terms of setvbuf().  The #define is correctly
ifdefed in some places but was not correctly ifdefed here -- i.e., BSD
was essentially configured as USG here.  This became fatal when <stdio.h>
was de-__P(())ified without testing.  This file gets included before
<stdio.h>, so the #define now affects (and breaks)
`setbuffer<left parentheses>' in <stdio.h> where it didn't affect
`setbuffer<whitespace>'.

gnu/usr.bin/as/config/ho-sysv.h

@@ -21,7 +21,9 @@
 
 #define HO_USG
 
+#ifdef USG
 #define setbuffer(stream, buf, size) setvbuf((stream), (buf), _IOLBF, (size))
+#endif
 
 extern int free();
 extern char *malloc();