rename fds savefile from ".fds" to ".sav"...

to avoid accidental overwrite of rom if save folder is not set and defaults to rom folder for saves.
"fceumm saves fds savefile as a copy of the original rom with the save information"

src/general.c

@@ -95,7 +95,7 @@ char *FCEU_MakeFName(int type, int id1, char *cd1)
             sprintf(tmp, "%s"PSS "gameinfo"PSS "%s.pal", BaseDirectory, FileBase);
          break;
       case FCEUMKF_FDS:
-            sprintf(tmp, "%s"PSS "%s.fds", SaveDirectory, FileBase);
+            sprintf(tmp, "%s"PSS "%s.sav", SaveDirectory, FileBase);
          break;
       default:
          break;