using unsafe to optimize code

Author: oldrev

GeographicLib/Directory.Build.props

@@ -4,7 +4,7 @@
     <PackageId>Sandwych.GeographicLib</PackageId>
     <Title>This is an attempt to port the Java version of GeographicLib to C#.</Title>
     <PackageTags>geographic;gis;geodesic;gnomonic;</PackageTags>
-    <VersionPrefix>1.49.2</VersionPrefix>
+    <VersionPrefix>1.49.3</VersionPrefix>
   </PropertyGroup>
 
   <Import Project="../Shared.props" />

GeographicLib/GeoMath.cs

@@ -187,6 +187,22 @@ public static double Polyval(int N, double[] p, int s, double x)
             return y;
         }
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static double Polyval(int N, in ReadOnlySpan<double> p, int s, double x)
+        {
+            double y = N < 0 ? 0 : p[s++];
+            while (--N >= 0) y = y * x + p[s++];
+            return y;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public unsafe static double Polyval(int N, double* p, int s, double x)
+        {
+            double y = N < 0 ? 0 : p[s++];
+            while (--N >= 0) y = y * x + p[s++];
+            return y;
+        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static double AngRound(double x)
         {
@@ -267,6 +283,7 @@ public static Pair AngDiff(double x, double y)
          * The results obey exactly the elementary properties of the trigonometric
          * functions, e.g., sin 9&deg; = cos 81&deg; = &minus; sin 123456789&deg;.
          **********************************************************************/
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static Pair Sincosd(double x)
         {
             // In order to minimize round-off errors, this function exactly reduces
@@ -303,6 +320,7 @@ public static Pair Sincosd(double x)
          * &minus;1) = &minus;180&deg;, for &epsilon; positive and tiny;
          * atan2d(&plusmn;0, 1) = &plusmn;0&deg;.
          **********************************************************************/
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static double Atan2d(double y, double x)
         {
             // In order to minimize round-off errors, this function rearranges the