AC_PID: revert AP_Math class change

libraries/AC_PID/AC_HELI_PID.cpp

@@ -56,7 +56,7 @@ float AC_HELI_PID::get_ff(float requested_rate) const
 
 float AC_HELI_PID::get_leaky_i(float leak_rate)
 {
-	if(!AP_Math::is_zero(_ki) && !AP_Math::is_zero(_dt)){
+	if(!is_zero(_ki) && !is_zero(_dt)){
 		_integrator -= (float)_integrator * leak_rate;
 		_integrator += ((float)_input * _ki) * _dt;
 		if (_integrator < -_imax) {

libraries/AC_PID/AC_PID.cpp

@@ -132,7 +132,7 @@ float AC_PID::get_p() const
 
 float AC_PID::get_i()
 {
-    if(!AP_Math::is_zero(_ki) && !AP_Math::is_zero(_dt)) {
+    if(!is_zero(_ki) && !is_zero(_dt)) {
         _integrator += ((float)_input * _ki) * _dt;
         if (_integrator < -_imax) {
             _integrator = -_imax;
@@ -199,7 +199,7 @@ void AC_PID::operator() (float p, float i, float d, float imaxval, float input_f
 // calc_filt_alpha - recalculate the input filter alpha
 float AC_PID::get_filt_alpha() const
 {
-    if (AP_Math::is_zero(_filt_hz)) {
+    if (is_zero(_filt_hz)) {
         return 1.0f;
     }
 

libraries/AC_PID/AC_PI_2D.cpp

@@ -95,7 +95,7 @@ Vector2f AC_PI_2D::get_p() const
 
 Vector2f AC_PI_2D::get_i()
 {
-    if(!AP_Math::is_zero(_ki) && !AP_Math::is_zero(_dt)) {
+    if(!is_zero(_ki) && !is_zero(_dt)) {
         _integrator += (_input * _ki) * _dt;
         float integrator_length = _integrator.length();
         if ((integrator_length > _imax) && (integrator_length > 0)) {
@@ -109,7 +109,7 @@ Vector2f AC_PI_2D::get_i()
 // get_i_shrink - get_i but do not allow integrator to grow in length (it may shrink)
 Vector2f AC_PI_2D::get_i_shrink()
 {
-    if (!AP_Math::is_zero(_ki) && !AP_Math::is_zero(_dt)) {
+    if (!is_zero(_ki) && !is_zero(_dt)) {
         float integrator_length_orig = min(_integrator.length(),_imax);
         _integrator += (_input * _ki) * _dt;
         float integrator_length_new = _integrator.length();
@@ -167,7 +167,7 @@ void AC_PI_2D::operator() (float p, float i, float imaxval, float input_filt_hz,
 // calc_filt_alpha - recalculate the input filter alpha
 void AC_PI_2D::calc_filt_alpha()
 {
-    if (AP_Math::is_zero(_filt_hz)) {
+    if (is_zero(_filt_hz)) {
         _filt_alpha = 1.0f;
         return;
     }