remove unnecessary cast from MakeLightTable

Also changed the c-style cast to static_cast with appropriate type for destination.

Source/lighting.cpp

@@ -919,10 +919,9 @@ void MakeLightTable()
 		for (int i = 0; i < 8; i++) {
 			for (int k = 0; k < 16; k++) {
 				for (int l = 0; l < 16; l++) {
-					double fs = (BYTE)sqrt((double)(8 * l - j) * (8 * l - j) + (8 * k - i) * (8 * k - i));
-					fs += fs < 0 ? -0.5 : 0.5;
-
-					lightblock[j * 8 + i][k][l] = fs;
+					int a = (8 * l - j);
+					int b = (8 * k - i);
+					lightblock[j * 8 + i][k][l] = static_cast<uint8_t>(sqrt(a * a + b * b));
 				}
 			}
 		}