Remove unused variables and functions

We remove the unused variables altogether, and port
libgd/libgd@f50c24e to silence the
compiler warnings.

Author: cmb69

ext/gd/libgd/gd_interpolation.c

@@ -366,6 +366,7 @@ static double filter_generalized_cubic(const double t)
 	return 0;
 }
 
+#ifdef FUNCTION_NOT_USED_YET
 /* CubicSpline filter, default radius 2 */
 static double filter_cubic_spline(const double x1)
 {
@@ -381,7 +382,9 @@ static double filter_cubic_spline(const double x1)
 	}
 	return 0;
 }
+#endif
 
+#ifdef FUNCTION_NOT_USED_YET
 /* CubicConvolution filter, default radius 3 */
 static double filter_cubic_convolution(const double x1)
 {
@@ -394,6 +397,7 @@ static double filter_cubic_convolution(const double x1)
 	if (x <= 3.0) return ( (1.0/12.0) * x2_x - (2.0 / 3.0) * x2 + 1.75 * x - 1.5);
 	return 0;
 }
+#endif
 
 static double filter_box(double x) {
 	if (x < - DEFAULT_FILTER_BOX)
@@ -418,15 +422,17 @@ static double filter_catmullrom(const double x)
 	return(0.0f);
 }
 
+#ifdef FUNCTION_NOT_USED_YET
 static double filter_filter(double t)
 {
 	/* f(t) = 2|t|^3 - 3|t|^2 + 1, -1 <= t <= 1 */
 	if(t < 0.0) t = -t;
 	if(t < 1.0) return((2.0 * t - 3.0) * t * t + 1.0);
 	return(0.0);
 }
+#endif
 
-
+#ifdef FUNCTION_NOT_USED_YET
 /* Lanczos8 filter, default radius 8 */
 static double filter_lanczos8(const double x1)
 {
@@ -441,8 +447,9 @@ static double filter_lanczos8(const double x1)
 	return 0.0;
 #undef R
 }
+#endif
 
-
+#ifdef FUNCTION_NOT_USED_YET
 /* Lanczos3 filter, default radius 3 */
 static double filter_lanczos3(const double x1)
 {
@@ -458,6 +465,7 @@ static double filter_lanczos3(const double x1)
 	return 0.0;
 #undef R
 }
+#endif
 
 /* Hermite filter, default radius 1 */
 static double filter_hermite(const double x1)
@@ -515,13 +523,15 @@ static double filter_mitchell(const double x)
 
 
 
+#ifdef FUNCTION_NOT_USED_YET
 /* Cosine filter, default radius 1 */
 static double filter_cosine(const double x)
 {
 	if ((x >= -1.0) && (x <= 1.0)) return ((cos(x * M_PI) + 1.0)/2.0);
 
 	return 0;
 }
+#endif
 
 /* Quadratic filter, default radius 1.5 */
 static double filter_quadratic(const double x1)
@@ -553,6 +563,7 @@ static double filter_bspline(const double x)
 	}
 }
 
+#ifdef FUNCTION_NOT_USED_YET
 /* QuadraticBSpline filter, default radius 1.5 */
 static double filter_quadratic_bspline(const double x1)
 {
@@ -562,6 +573,7 @@ static double filter_quadratic_bspline(const double x1)
 	if (x <= 1.5) return (0.5 * x * x - 1.5 * x + 1.125);
 	return 0.0;
 }
+#endif
 
 static double filter_gaussian(const double x)
 {
@@ -603,14 +615,15 @@ static double filter_sinc(const double x)
 	return (sin(M_PI * (double) x) / (M_PI * (double) x));
 }
 
+#ifdef FUNCTION_NOT_USED_YET
 static double filter_welsh(const double x)
 {
 	/* Welsh parabolic windowing filter */
 	if (x <  1.0)
 		return(1 - x*x);
 	return(0.0);
 }
-
+#endif
 
 /* Copied from upstream's libgd */
 static inline int _color_blend (const int dst, const int src)
@@ -1287,7 +1300,6 @@ static gdImagePtr gdImageScaleBilinearTC(gdImagePtr im, const unsigned int new_w
 
 	int dst_offset_h;
 	int dst_offset_v = 0;
-	int dwSrcTotalOffset;
 	long i;
 	gdImagePtr new_img;
 
@@ -1326,7 +1338,6 @@ static gdImagePtr gdImageScaleBilinearTC(gdImagePtr im, const unsigned int new_w
 					f_g1, f_g2, f_g3, f_g4,
 					f_b1, f_b2, f_b3, f_b4,
 					f_a1, f_a2, f_a3, f_a4;
-			dwSrcTotalOffset = m + n;
 			/* 0 for bgColor; (n,m) is supposed to be valid anyway */
 			pixel1 = getPixelOverflowTC(im, n, m, 0);
 			pixel2 = getPixelOverflowTC(im, n + 1, m, pixel1);
@@ -2352,12 +2363,10 @@ int gdTransformAffineCopy(gdImagePtr dst,
 	gdRect bbox;
 	int end_x, end_y;
 	gdInterpolationMethod interpolation_id_bak = GD_DEFAULT;
-	interpolation_method interpolation_bak;
 
 	/* These methods use special implementations */
 	if (src->interpolation_id == GD_BILINEAR_FIXED || src->interpolation_id == GD_BICUBIC_FIXED || src->interpolation_id == GD_NEAREST_NEIGHBOUR) {
 		interpolation_id_bak = src->interpolation_id;
-		interpolation_bak = src->interpolation;
 
 		gdImageSetInterpolationMethod(src, GD_BICUBIC);
 	}