motion: add ability to have gcode s0 while m3/4 is active

Usually in linuxcnc, setting s0 would set spindle off;
Setting m3/4 before s was above 0 would not allow s to be set after.
This commit fixes those problems.
tested on a real machine with two spinldes - one as an indexer

It's common in other machines to be able to set S and m3/4/5 separately.
This allows using the extra spindles in unique ways such as indexers.
(s setting can represent position)
This may help laser users with laser intensity etc.

If users relied on setting s to 0 to turn off the spindle will need to change their programs.
One could argue the were not using the code properly anyways.

src/emc/motion/command.c

@@ -1770,6 +1770,8 @@ void emcmotCommandHandler(void *arg, long period)
 	        /* 	tpAbort(&emcmotDebug->tp); */
 	        /* 	SET_MOTION_ERROR_FLAG(1); */
 	        /* } else {...} */
+	        rtapi_print( "command state %d\n", emcmotCommand->state);
+	        emcmotStatus->spindle_status[n].state = emcmotCommand->state;
 	        emcmotStatus->spindle_status[n].speed = emcmotCommand->vel;
 	        emcmotStatus->spindle_status[n].css_factor = emcmotCommand->ini_maxvel;
 	        emcmotStatus->spindle_status[n].xoffset = emcmotCommand->acc;
@@ -1804,6 +1806,7 @@ void emcmotCommandHandler(void *arg, long period)
         }
         for (n = s0; n<=s1; n++){
 
+	        emcmotStatus->spindle_status[n].state = 0;
 	        emcmotStatus->spindle_status[n].speed = 0;
 	        emcmotStatus->spindle_status[n].direction = 0;
 	        emcmotStatus->spindle_status[n].brake = 1; // engage brake

src/emc/motion/control.c

@@ -1897,7 +1897,7 @@ static void output_to_hal(void)
 		*(emcmot_hal_data->spindle[spindle_num].spindle_speed_cmd_rps) =
 				emcmotStatus->spindle_status[spindle_num].speed / 60.;
 		*(emcmot_hal_data->spindle[spindle_num].spindle_on) =
-				((emcmotStatus->spindle_status[spindle_num].speed *
+				((emcmotStatus->spindle_status[spindle_num].state *
 						emcmotStatus->spindle_status[spindle_num].net_scale) != 0) ? 1 : 0;
 		*(emcmot_hal_data->spindle[spindle_num].spindle_forward) =
 				(*emcmot_hal_data->spindle[spindle_num].spindle_speed_out > 0) ? 1 : 0;

src/emc/motion/motion.h

@@ -262,6 +262,7 @@ extern "C" {
     int probe_home_err_inhibit;  // setting to inhibit probe tripped while homeing error.
     EmcPose tool_offset;        /* TLO */
     double  orientation;    /* angle for spindle orient */
+    int state; /*spindle state*/
     char    direction;      /* CANON_DIRECTION flag for spindle orient */
     double  timeout;        /* of wait for spindle orient to complete */
     unsigned char wait_for_spindle_at_speed; // EMCMOT_SPINDLE_ON now carries this, for next feed move
@@ -544,6 +545,7 @@ Suggestion: Split this in to an Error and a Status flag register..
 	double net_scale;   // scale or zero if inhibited
 	double css_factor;
 	double xoffset;
+	int state;
 	int direction;		// 0 stopped, 1 forward, -1 reverse
 	int brake;		// 0 released, 1 engaged
 	int locked;             // spindle lock engaged after orient

src/emc/nml_intf/emc_nml.hh

@@ -1197,6 +1197,7 @@ class EMC_SPINDLE_STAT:public EMC_SPINDLE_STAT_MSG {
     double spindle_scale;	// spindle over-ride
     double css_maximum;
     double css_factor;  // CSS Status
+    int state;
     int direction;		// 0 stopped, 1 forward, -1 reverse
     int brake;			// 0 released, 1 engaged
     int increasing;		// 1 increasing, -1 decreasing, 0 neither

src/emc/task/taskintf.cc

@@ -1840,10 +1840,12 @@ int emcSpindleAbort(int spindle)
 
 int emcSpindleSpeed(int spindle, double speed, double css_factor, double offset)
 {
-    if (emcmotStatus.spindle_status[spindle].speed == 0){
+    emcmotCommand.command = EMCMOT_SPINDLE_ON;
-        return 0;} //spindle stopped, not updating speed */
+    emcmotCommand.spindle = spindle;
-
+    emcmotCommand.vel = speed;
-    return emcSpindleOn(spindle, speed, css_factor, offset);
+    emcmotCommand.ini_maxvel = css_factor;
+    emcmotCommand.acc = offset;
+    return usrmotWriteEmcmotCommand(&emcmotCommand);
 }
 
 int emcSpindleOrient(int spindle, double orientation, int mode)
@@ -1858,9 +1860,9 @@ int emcSpindleOrient(int spindle, double orientation, int mode)
 
 int emcSpindleOn(int spindle, double speed, double css_factor, double offset, int wait_for_at_speed)
 {
-
     emcmotCommand.command = EMCMOT_SPINDLE_ON;
     emcmotCommand.spindle = spindle;
+    emcmotCommand.state = 1;
     emcmotCommand.vel = speed;
     emcmotCommand.ini_maxvel = css_factor;
     emcmotCommand.acc = offset;
@@ -1871,6 +1873,7 @@ int emcSpindleOn(int spindle, double speed, double css_factor, double offset, in
 int emcSpindleOff(int spindle)
 {
     emcmotCommand.command = EMCMOT_SPINDLE_OFF;
+    emcmotCommand.state = 0;
     emcmotCommand.spindle = spindle;
     return usrmotWriteEmcmotCommand(&emcmotCommand);
 }