fix breakage from introducing bits header for sys/io.h

apparently some other archs have sys/io.h and should not break just
because they don't have the x86 port io functions. provide a blank
bits/io.h everywhere for now.

include/sys/io.h

@@ -8,6 +8,9 @@ extern "C" {
 
 #include <bits/io.h>
 
+int iopl(int);
+int ioperm(unsigned long, unsigned long, int);
+
 #ifdef __cplusplus
 }
 #endif