Make run faster on ARM CPUs using fast math approximation

Use --fast-math to use sine/cosine tables and approximate atan2.

src/nmt/main.c

@@ -381,7 +381,8 @@ int main(int argc, char *argv[])
 	if (!loopback)
 		print_image();
 
-	/* init functions */
+	/* inits */
+	fm_init(fast_math);
 	rc = init_frame();
 	if (rc < 0) {
 		fprintf(stderr, "Failed to setup frames. Quitting!\n");
@@ -419,6 +420,9 @@ fail:
 	while (sender_head)
 		nmt_destroy(sender_head);
 
+	/* exits */
+	fm_exit();
+
 	return 0;
 }