improve Makefile, README.md, .gitignore, code, bugs.md for 2004/gavin

2004/gavin/gavin.c

@@ -1,8 +1,9 @@
+int main(int t, char **q, char **d) { return cain(t, (int)q, (int)d); }
 #define G(n) int n(int t, int q, int d)
 #define X(p,t,s) (p>=t&&p<(t+s)&&(p-(t)&1023)<(s&1023))
 #define U(m) *((signed char *)(m))
 #define F if(!--q){
-#define I(s) (int)main-(int)s
+#define I(s) (int)cain-(int)s
 #define P(s,c,k) for(h=0; h>>14==0; h+=129)Y(16*c+h/1024+Y(V+36))&128>>(h&7)?U(s+(h&15367))=k:k
 
 G (B)
@@ -52,7 +53,7 @@ else
 
 G (_);
 G (o);
-G (main)
+G (cain)
 {
   Z, k = K;
   if (!t)