XXX Rearchitect and replace interrupt distribution

*** 48,57 ****
--- 48,58 ----
  #define A_FTRACE        15
  #define A_SWAPCTL       16
  /*                      17-21      reserved for obsolete interface */
  #define A_SDTTEST       22      /* DTrace sdt:::test */
  #define A_CONFIG        23      /* For system configuration */
+ #define A_INTRD         24      /* Interrupt balancer */
  
  #define AD_UNKNOWN      -1      /* no method */
  #define AD_HALT         0       /* halt the processor */
  #define AD_BOOT         1       /* multi-user reboot */
  #define AD_IBOOT        2       /* multi-user reboot, ask for name of file */