solved some compiler warnings that are now visible in arduino 1.0.

Found a couple of unused variables, that I commented.
Tried to solve the program memory warning message, and failed.

Marlin/cardreader.pde

@@ -40,7 +40,7 @@ char *createFilename(char *buffer,const dir_t &p) //buffer>12characters
 }
 
 
-void  CardReader::lsDive(char *prepend,SdFile parent)
+void  CardReader::lsDive(const char *prepend,SdFile parent)
 {
   dir_t p;
  uint8_t cnt=0;