Do not define CFLAGS

--- a/src/Makefile.am	2005-06-29 14:14:02.000000000 +0200
+++ b/src/Makefile.am	2009-04-28 18:18:26.000000000 +0200
@@ -18,7 +18,7 @@
               smb-ext.c smb-ext.h
 
 smbc_CFLAGS = -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -Wall
-CFLAGS = -O3
+#CFLAGS = -O3
 
 if GDB
   smbc_CFLAGS += -ggdb -g