Fix bug reported by Daniel Lertpratchya <nikkipui@gmail.com>:

On Dec 6, 2013, at 8:28 AM, Daniel Lertpratchya <nikkipui@gmail.com>
 wrote:
I recently ran the doxygen.warnings.report.sh script and I got the
following error. I tried on a fresh copy of ns-3-dev and Brian
also has the same problem.

'build' finished successfully (1.649s)

Rebuilding doxygen docs with full errors...Done.
mv: missing destination file operand after ‘doc/doxygen.log’
Try 'mv --help' for more information.
No filters.

cat: doc/doxygen.warnings.log: No such file or directory
grep: doc/doxygen.warnings.log: No such file or directory
cat: doc/doxygen.warnings.log: No such file or directory

On Dec 6, 2013, at 10:36 AM, Daniel Lertpratchya <nikkipui@gmail.com>
 wrote:
I think doxygen.warnings.report.sh line 150 should be changed from
$log to $LOG. That seems to fix the problem for me.

doc/doxygen.warnings.report.sh

@@ -147,7 +147,7 @@ else
 	exit 1
     fi
 
-    mv $DIR/doxygen.log $log
+    mv $DIR/doxygen.log $LOG
 
 fi