AP_Math: add casts to consider literals as doubles

Since we pass -fsingle-precision-constant to the compiler, add casts to
make literals real doubles.

libraries/AP_Math/location.cpp

@@ -202,7 +202,7 @@ void print_latlon(AP_HAL::BetterStream *s, int32_t lat_or_lon)
 
 void wgsllh2ecef(const Vector3d &llh, Vector3d &ecef) {
   double d = WGS84_E * sin(llh[0]);
-  double N = WGS84_A / sqrt(1. - d*d);
+  double N = WGS84_A / sqrt(1 - d*d);
 
   ecef[0] = (N + llh[2]) * cos(llh[0]) * cos(llh[1]);
   ecef[1] = (N + llh[2]) * cos(llh[0]) * sin(llh[1]);
@@ -222,7 +222,7 @@ void wgsecef2llh(const Vector3d &ecef, Vector3d &llh) {
 
   /* If we are close to the pole then convergence is very slow, treat this is a
    * special case. */
-  if (p < WGS84_A*1e-16) {
+  if (p < WGS84_A * double(1e-16)) {
     llh[0] = copysign(M_PI_2, ecef[2]);
     llh[2] = fabs(ecef[2]) - WGS84_B;
     return;
@@ -230,7 +230,7 @@ void wgsecef2llh(const Vector3d &ecef, Vector3d &llh) {
 
   /* Calculate some other constants as defined in the Fukushima paper. */
   const double P = p / WGS84_A;
-  const double e_c = sqrt(1. - WGS84_E*WGS84_E);
+  const double e_c = sqrt(1 - WGS84_E*WGS84_E);
   const double Z = fabs(ecef[2]) * e_c / WGS84_A;
 
   /* Initial values for S and C correspond to a zero height solution. */
@@ -253,7 +253,7 @@ void wgsecef2llh(const Vector3d &ecef, Vector3d &llh) {
     A_n = sqrt(S*S + C*C);
     D_n = Z*A_n*A_n*A_n + WGS84_E*WGS84_E*S*S*S;
     F_n = P*A_n*A_n*A_n - WGS84_E*WGS84_E*C*C*C;
-    B_n = 1.5*WGS84_E*S*C*C*(A_n*(P*S - Z*C) - WGS84_E*S*C);
+    B_n = double(1.5) * WGS84_E*S*C*C*(A_n*(P*S - Z*C) - WGS84_E*S*C);
 
     /* Update step. */
     S = D_n*F_n - B_n*S;
@@ -289,7 +289,7 @@ void wgsecef2llh(const Vector3d &ecef, Vector3d &llh) {
     }
 
     /* Check for convergence and exit early if we have converged. */
-    if (fabs(S - prev_S) < 1e-16 && fabs(C - prev_C) < 1e-16) {
+    if (fabs(S - prev_S) < double(1e-16) && fabs(C - prev_C) < double(1e-16)) {
       break;
     } else {
       prev_S = S;