Joystick support fixes.

I did this because I wanted to fly around maps using a Spaceball
4000FLX, or any other 6DOF controller.  These fixes help it work.

Various fixes to joystick support:
  - joyaxiscallback() used strtol() to check to see if the supplied
    string was an integer, then didn't assign the parsed integer to
    the cvar.
  - Wrong multiplier for left/turnleft values.
  - Delete `axismap[]` from J_JoystickAxis().  It was causing problems,
    and smells like it was trying to do what the cvars
    joyadvaxis[xyzruv] are doing now.
  - Fix compiler error by adding case statements for:
	SDL_SENSOR_ACCEL_L
	SDL_SENSOR_ACCEL_R
	SDL_SENSOR_GYRO_L
	SDL_SENSOR_GYRO_R

New cvar: "joyonly".

"Joystick" axes are typically return-to-center affairs; their deflection
values are therefore reported as -MAX - MAX, with zero in the center.
"Game controllers" are similar, but also often have analog left and
right "triggers" which are reported as 0 - MAX, with zero at one end
(fully released to fully depressed).

Unfortunately, SDL will try its darndest to make a joystick look like a
"game controller."  It does this by reinterpreting certain of the axes
to report the range 0 - MAX, as if they were triggers.  This is not a
thing to do with 6DOF controllers, where all axes are return-to-center.
While it may be remotely possible to put together an SDL2 controller
mapping that reports -MAX - MAX on all axes, for me it was simpler to
hack on FTEQW.

Coupled with that is FTEQW's giving preference to "game controllers,"
i.e. if SDL_IsGameController() returns true, FTEQW will treat it as one.

"joyonly" is a boolean cvar.  If true, FTE will ignore "game
controllers" and treat everything as a joystick.  The default is false.
"joyonly" must be set at startup to be effective, when the controllers
are being enumerated by SDL.

engine/client/in_generic.c

@@ -31,9 +31,15 @@ void QDECL joyaxiscallback(cvar_t *var, char *oldvalue)
 {
 	int sign;
 	char *end;
-	strtol(var->string, &end, 0);
+	sign = strtol(var->string, &end, 0);
-	if (!*end)	//okay, its missing or an actual number.
+	if (!*end)
+	{
+		//okay, its missing or an actual number.
+		if (sign >= -6  &&  sign <= 6) {
+			var->ival = sign;
+		}
 		return;
+	}
 
 	end = var->string;
 	if (*end == '-')
@@ -63,7 +69,7 @@ void QDECL joyaxiscallback(cvar_t *var, char *oldvalue)
 	else if (!Q_strcasecmp(end, "right") || !Q_strcasecmp(end, "turnright"))
 		var->ival = 4*sign;
 	else if (!Q_strcasecmp(end, "left") || !Q_strcasecmp(end, "turnleft"))
-		var->ival = 4*sign*1;
+		var->ival = 4*sign*-1;
 	else if (!Q_strcasecmp(end, "up") || !Q_strcasecmp(end, "moveup"))
 		var->ival = 5*sign;
 	else if (!Q_strcasecmp(end, "down") || !Q_strcasecmp(end, "movedown"))

engine/client/in_sdl.c

@@ -95,6 +95,9 @@ static uint32_t SDL_GiveFinger(SDL_JoystickID jid, SDL_TouchID tid, SDL_FingerID
 
 #if SDL_MAJOR_VERSION >= 2
 #define MAX_JOYSTICKS 16
+#ifndef MAXJOYAXIS
+#define MAXJOYAXIS 6
+#endif
 
 static struct
 {
@@ -154,6 +157,8 @@ static struct sdljoy_s
 	float buttonrepeat[countof(gpbuttonmap)];
 } sdljoy[MAX_JOYSTICKS]; 
 
+static cvar_t joy_only = CVARD("joyonly", "0", "If true, treats \"game controllers\" as regular joysticks.\nMust be set at startup.");
+
 //the enumid is the value for the open function rather than the working id.
 static void J_AllocateDevID(struct sdljoy_s *joy)
 {
@@ -184,6 +189,10 @@ static void J_ControllerAdded(int enumid)
 {
 	const char *cname;
 	int i;
+
+	if (joy_only.ival)
+		return;
+
 	for (i = 0; i < MAX_JOYSTICKS; i++)
 		if (sdljoy[i].controller == NULL && sdljoy[i].joystick == NULL)
 			break;
@@ -213,7 +222,7 @@ static void J_JoystickAdded(int enumid)
 	if (i == MAX_JOYSTICKS)
 		return;
 
-	if (SDL_IsGameController(enumid))	//if its reported via the gamecontroller api then use that instead. don't open it twice.
+	if (!joy_only.ival  &&  SDL_IsGameController(enumid))	//if its reported via the gamecontroller api then use that instead. don't open it twice.
 		return;
 
 	sdljoy[i].joystick = SDL_JoystickOpen(enumid);
@@ -283,11 +292,17 @@ static void J_ControllerAxis(SDL_JoystickID jid, int axis, int value)
 }
 static void J_JoystickAxis(SDL_JoystickID jid, int axis, int value)
 {
-	static const int axismap[] = {0,1,3,4,2,5};
-
 	struct sdljoy_s *joy = J_DevId(jid);
-	if (joy && !joy->controller && axis < sizeof(axismap)/sizeof(axismap[0]) && joy->qdevid != DEVID_UNSET)
+
-		IN_JoystickAxisEvent(joy->qdevid, axismap[axis], value / 32767.0);
+	if (joy->qdevid == DEVID_UNSET)
+	{
+		if (abs(value) < 0x1000)
+			return;
+		J_AllocateDevID(joy);
+	}
+
+	if (joy && !joy->controller && axis < MAXJOYAXIS && joy->qdevid != DEVID_UNSET)
+		IN_JoystickAxisEvent(joy->qdevid, axis, value / 32767.0);
 }
 //we don't do hats and balls and stuff.
 static void J_ControllerButton(SDL_JoystickID jid, int button, qboolean pressed)
@@ -499,6 +514,10 @@ static void J_ControllerSensor(SDL_JoystickID jid, SDL_SensorType sensor, float
 	case SDL_SENSOR_GYRO:
 		IN_Gyroscope(joy->qdevid, data[0], data[1], data[2]);
 		break;
+	case SDL_SENSOR_ACCEL_L:
+	case SDL_SENSOR_ACCEL_R:
+	case SDL_SENSOR_GYRO_L:
+	case SDL_SENSOR_GYRO_R:
 	case SDL_SENSOR_INVALID:
 	case SDL_SENSOR_UNKNOWN:
 	safedefault:
@@ -1454,6 +1473,7 @@ void INS_Init (void)
 #ifdef HAVE_SDL_TEXTINPUT
 	Cvar_Register(&sys_osk, "input controls");
 #endif
+	Cvar_Register (&joy_only, "input controls");
 
 #ifdef HAVE_SDL_TEXTINPUT
 #ifdef __linux__