Dump/undump reuse strings

A repeated string in a dump is represented as an index to its first
occurence, instead of another copy of the string.

lundump.h

@@ -31,6 +31,6 @@ LUAI_FUNC LClosure* luaU_undump (lua_State* L, ZIO* Z, const char* name);
 
 /* dump one chunk; from ldump.c */
 LUAI_FUNC int luaU_dump (lua_State* L, const Proto* f, lua_Writer w,
-                         void* data, int strip);
+                         void* data, int strip, Table *h);
 
 #endif