Homing and limit updates. Minor bug fixes.

- Updated new homing cycle to error out when a pull-off motion detects
the limit is still active.

- Created a limits_get_state() function to centralize it. It reports
state as a bit-wise booleans according to axis numbering.

- Updated the print uint8 functions. Generalized it to allow both base2
and base10 printouts, while allowing base2 prints with N_AXIS digits
for limit state status reports. Doing this saved about 100bytes of
flash as well.

- Applied CoreXY status reporting bug fix by @phd0. Thanks!

grbl/report.c

@@ -496,10 +496,7 @@ void report_realtime_status()
   
   if (bit_istrue(settings.status_report_mask,BITFLAG_RT_STATUS_LIMIT_PINS)) {
     printPgmString(PSTR(",Lim:"));
-    for (idx=0; idx<N_AXIS; idx++) {
-      if (LIMIT_PIN & get_limit_pin_mask(idx)) { printPgmString(PSTR("1")); }
-      else { printPgmString(PSTR("0")); }
-    }
+    print_unsigned_int8(limits_get_state(),2,N_AXIS);
   }
   
   #ifdef REPORT_CONTROL_PIN_STATE