Compiler optimization back to '-O2'

Undo commit 6a10f03ff. Compiler performance is important, too.
diff --git a/makefile b/makefile
index 7af5533..9e537dc 100644
--- a/makefile
+++ b/makefile
@@ -109,16 +109,6 @@
 	$(CC) -o $@ $(MYLDFLAGS) $(LUA_O) $(CORE_T) $(LIBS) $(MYLIBS) $(DL)
 
 
-llex.o:
-	$(CC) $(CFLAGS) -Os -c llex.c
-
-lparser.o:
-	$(CC) $(CFLAGS) -Os -c lparser.c
-
-lcode.o:
-	$(CC) $(CFLAGS) -Os -c lcode.c
-
-
 clean:
 	$(RM) $(ALL_T) $(ALL_O)