Fix T43450: Texture node tree failed to clamp

Clamping routine was not implemented. This fixes T43450.

Reviewers: #nodes, #rendering, sergey

Reviewed By: sergey

Maniphest Tasks: T43450

Differential Revision: https://developer.blender.org/D1038

source/blender/nodes/texture/nodes/node_texture_math.c

@@ -195,6 +195,10 @@ static void valuefn(float *out, TexParams *p, bNode *node, bNodeStack **in, shor
 			break;
 		}
 	}
+
+	if (node->custom2 & SHD_MATH_CLAMP) {
+		CLAMP(*out, 0.0f, 1.0f);
+	}
 }
 
 static void exec(void *data, int UNUSED(thread), bNode *node, bNodeExecData *execdata, bNodeStack **in, bNodeStack **out)