Build with -Wfloat-conversion + fix all warnings

test/testffmpeg.c

@@ -1492,7 +1492,7 @@ int main(int argc, char *argv[])
         positions[i].h = (float)sprite_h;
         velocities[i].x = 0.0f;
         velocities[i].y = 0.0f;
-        while (!velocities[i].x || !velocities[i].y) {
+        while (velocities[i].x == 0.f || velocities[i].y == 0.f) {
             velocities[i].x = (float)((rand() % (2 + 1)) - 1);
             velocities[i].y = (float)((rand() % (2 + 1)) - 1);
         }