Remove perlin noise helper functions that are no longer used

src/SeExpr/SeExprBuiltins.cpp

@@ -32,20 +32,6 @@
 
 namespace SeExpr {
 
-
-namespace {
-    // helper functions used by perlin()
-    inline double fade(double t) { return t*t*t*(t*(t*6-15)+10); }
-    inline double lerp(double t, double a, double b) { return a+t*(b-a); }
-    inline double grad(int hash, double x, double y, double z) {
-	int h = hash & 15;              // CONVERT LO 4 BITS OF HASH CODE
-	double u = h<8 ? x : y,         // INTO 12 GRADIENT DIRECTIONS.
-	    v = h<4 ? y : h==12||h==14 ? x : z;
-	return ((h&1) == 0 ? u : -u) + ((h&2) == 0 ? v : -v);
-    }
-}
-
-
 static const char* fabs_docstring="float abs(float x)\nabsolute value of x";
 
 // angle conversion functions