I removed an additional #include <math.h>

I found an additional "#include <math.h>" so I removed it.
Thinking that it was additional.

demo/allegro5/main.c

@@ -6,7 +6,6 @@
 #include <string.h>
 #include <math.h>
 #include <assert.h>
-#include <math.h>
 #include <limits.h>
 #include <time.h>