Added the following tests:

 * Single point overlaps
  * Tree: {|0-1|}, query of |1-2| returns |0-1|
  * Tree: {|1-2|}, query of |0-1| returns |1-2|
  * Tree: {|1-2|}, insert of of |0-1| success == allow_overlaps
  * Tree: {|0-1|}, insert of of |1-2| success == allow_overlaps
 * Complete overlaps
  * Tree: {|0-3|}, query of |1-2| returns |0-3|
  * Tree: {|1-2|}, query of |0-3| returns |1-2|
  * Tree: {|1-2|}, insert of of |0-3| success == allow_overlaps
  * Tree: {|0-3|}, insert of of |1-2| success == allow_overlaps
 * Exact overlaps
  * Tree: {|0-3|}, query of |0-3| returns |0-3|
  * Tree: {|0-3|}, insert of of |0-3| success == allow_overlaps

Also freed buf and NULLed the pointer to help find memory leaks.

git-svn-id: file:///svn/tokudb@1745 c7de825b-a66e-492c-adef-691d508d4ae1