Recast: move DT_PI constant to DetourMath.h

DT_PI is used in many places, and each implementation defines its own with the same value. This is the start to factor that into 1 constant.

src/thirdparty/recast/Detour/Include/DetourMath.h

@@ -12,6 +12,9 @@ Members in this module are wrappers around the standard math library
 // if cmath is included before math.h.
 #include <cmath>
 
+/// The value of PI used by Recast.
+static const float DT_PI = 3.14159265f;
+
 inline float dtMathFabsf(float x) { return fabsf(x); }
 inline float dtMathSqrtf(float x) { return sqrtf(x); }
 inline float dtMathFloorf(float x) { return floorf(x); }

src/thirdparty/recast/DetourCrowd/Source/DetourObstacleAvoidance.cpp

@@ -25,8 +25,6 @@
 #include <float.h>
 #include <new>
 
-static const float DT_PI = 3.14159265f;
-
 static int sweepCircleCircle(const float* c0, const float r0, const float* v,
 							 const float* c1, const float r1,
 							 float& tmin, float& tmax)