Introduce math.h

Makes fix for introducing 0.5 and 3.0 double constants into rels less hacky

include/math.h

@@ -0,0 +1,43 @@
+#ifndef _MATH_H
+#define _MATH_H
+
+extern inline float sqrtf(float x)
+{
+	static const double _half=.5;
+	static const double _three=3.0;
+	volatile float y;
+	if(x > 0.0f)
+	{
+		double guess = __frsqrte((double)x);   // returns an approximation to
+		guess = _half*guess*(_three - guess*guess*x);  // now have 12 sig bits
+		guess = _half*guess*(_three - guess*guess*x);  // now have 24 sig bits
+		guess = _half*guess*(_three - guess*guess*x);  // now have 32 sig bits
+		y=(float)(x*guess);
+		return y;
+	}
+	return x;
+}
+
+double atan(double x);
+double copysign(double x, double y);
+double cos(double x);
+double floor(double x);
+double frexp(double x, int *exp);
+double ldexp(double x, int exp);
+double modf(double x, double *intpart);
+double sin(double x);
+double tan(double x);
+double acos(double x);
+double asin(double x);
+double atan2(double y, double x);
+double fmod(double x, double y);
+double log(double x);
+float tanf(float x);
+float sinf(float x);
+float cosf(float x);
+float atan2f(float y, float x);
+float acosf(float x);
+
+#define abs(x) __abs(x)
+
+#endif