Fix for -fno-common

Index: src/snow.c
--- src/snow.c.orig
+++ src/snow.c
@@ -38,6 +38,14 @@
 
 #define NFLAKES 1000
 
+struct Flake{
+  float x,y;
+  float vx,vy;
+  float s;
+};
+
+struct Flake *flakes;
+
 
 void CreateSnow(int w,int h){
   int i;
