Minor optimization in high res sine wave (thanks Rob Tillaart)

http://forum.arduino.cc/index.php?topic=372960.msg2574826#msg2574826

synth_sine.cpp

 {
 	int32_t angle, sum, p1, p2, p3, p5, p7, p9, p11;
 
-	if (ph >= 0xC0000000 || ph < 0x40000000) {
+	if (ph >= 0xC0000000 || ph < 0x40000000) {                            // ph:  0.32
 		angle = (int32_t)ph; // valid from -90 to +90 degrees
 	} else {
-		angle = (int32_t)(0x80000000u - ph);
+		angle = (int32_t)(0x80000000u - ph);                        // angle: 2.30
 	}
-	p1 =  multiply_32x32_rshift32_rounded(angle << 1, 1686629713);
-	p2 =  multiply_32x32_rshift32_rounded(p1, p1) << 3;
-	p3 =  multiply_32x32_rshift32_rounded(p2, p1) << 3;
-	sum = multiply_subtract_32x32_rshift32_rounded(p1 << 1, p3, 1431655765);
-	p5 =  multiply_32x32_rshift32_rounded(p3, p2) << 1;
+	p1 =  multiply_32x32_rshift32_rounded(angle, 1686629713) << 2;        // p1:  2.30
+	p2 =  multiply_32x32_rshift32_rounded(p1, p1) << 1;                   // p2:  3.29
+	p3 =  multiply_32x32_rshift32_rounded(p2, p1) << 2;                   // p3:  3.29
+	sum = multiply_subtract_32x32_rshift32_rounded(p1, p3, 1431655765);   // sum: 2.30
+	p5 =  multiply_32x32_rshift32_rounded(p3, p2) << 1;                   // p5:  5.27
 	sum = multiply_accumulate_32x32_rshift32_rounded(sum, p5, 286331153);
-	p7 =  multiply_32x32_rshift32_rounded(p5, p2);
+	p7 =  multiply_32x32_rshift32_rounded(p5, p2);                        // p7:  8.24
 	sum = multiply_subtract_32x32_rshift32_rounded(sum, p7, 54539267);
-	p9 =  multiply_32x32_rshift32_rounded(p7, p2);
+	p9 =  multiply_32x32_rshift32_rounded(p7, p2);                        // p9: 11.21
 	sum = multiply_accumulate_32x32_rshift32_rounded(sum, p9, 6059919);
-	p11 = multiply_32x32_rshift32_rounded(p9, p2);
+	p11 = multiply_32x32_rshift32_rounded(p9, p2);                       // p11: 14.18
 	sum = multiply_subtract_32x32_rshift32_rounded(sum, p11, 440721);
-	return sum <<= 1;
+	return sum <<= 1;                                                 // return:  1.31
 }
 #endif