Use ff_sqrt() function instead of using a table

Originally committed as revision 13210 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/ra144.c

@@ -71,7 +71,7 @@ static int t_sqrt(unsigned int x)
         x = x >> 2;
     }
 
-    return (sqrt_table[x] << s) << 2;
+    return (ff_sqrt(x << 20) << s) << 2;
 }
 
 /* do 'voice' */