vlog: Introduce VLOG_DEFINE_THIS_MODULE for declaring vlog module in use.

Adding a macro to define the vlog module in use adds a level of
indirection, which makes it easier to change how the vlog module must be
defined.  A followup commit needs to do that, so getting these widespread
changes out of the way first should make that commit easier to review.

lib/svec.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010 Nicira Networks.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,10 +22,10 @@
 #include <string.h>
 #include "dynamic-string.h"
 #include "util.h"
-
-#define THIS_MODULE VLM_svec
 #include "vlog.h"
 
+VLOG_DEFINE_THIS_MODULE(svec)
+
 void
 svec_init(struct svec *svec)
 {